On Sunday, I flew my Mavic Air,  taking a video  (4k) for the first half of the flight, followed by a  couple of  panoramas. All seemed normal - as the recording was running, I  could see  the elapsed time counting on the Go4 display, so I assumed  it was  recording.
  
I had some videos on that SD card that were shot earlier in June,  in  addition to the 06/21/2020 videos. I did my usual copy of all the  changed files on the SD  card to a folder on my PC for storage, and all  seemed OK.
  
Yesterday, I got around to looking at the videos, all were there  EXCEPT  for the ones from 06/21/2020! I thought maybe somehow they got  recorded  to the internal storage on the MA, but I checked, and that was  not the case.
  
I scanned the SD card and internal storage with Rescuva  undelete  program, and there WERE deleted files on the SD card with  sizes that I  was expecting, and the prognosis for recovery were  Excellent. I restored  them all to a folder on my PC (nothing was  written to the SD card since  the flight on 06/21/2020).
  
Unfortunately, none of those files were playable, except for a small jpg thumbnail.
  
Has anyone encountered a situation like this? I looked at the  flight  record file with CSView, the camera data groups, and confirmed  that  recording was going on for the first half of the flight, followed  by the  panorama series. It would seem that the video file was  correctly  closed, since the recording was terminated normally, as  opposed to  letting the recording stop on its own when the drone shuts  down.
  
It looks like my only hope for these videos is to work with Rescuva  tech support to see what they suggest. Does anybody know of a better  undelete program for Win10?

I tried another undelete program, Disk Drill, and I did a quick scan, In the _DownloadCache_ folder, there are two  very large files. They appear to be the correct size, and the date/time  stamp has the date I took the video. They would be 4K MP4 files  (actually they seem to be copies..there was only one video taken that  day).

Does anyone understand how the the process that saves the videos works? Is this a temporary file?
Is there a way to determine what the filename would have been - i.e. what number would have been added?

How can I recover this into a valid MP4 file?

It would have shown \DFS\_DownloadCache_\DFS_Shop_BL_V1_4_X_X_DT2019_03_13_17_5_01_.7z

Why would such a large file be in a \DFS\ directory??  Every time I see video files, they are in \DCIM\100MEDIA

  

I suspect that the reason is still not in Mavic. To eliminate this in the future, try changing the SD card. Good luck

I thought these forums were monitored by DJI tech people.  This post was made almost a week ago, and I'm no closer to a solution to the problem of recovering the lost video file.  I have looked at the TXT file from my iPhone, and it's pretty clear that the recording was started,  and stopped several minutes before the end of the flight.

If there was an error in writing  the file to the SD card, would the drone's operating system not have noted the error...I've seen no such error.

The deleted file in the cache is a 7z extension, with is a compressed file archive.  It's too big to recover with the free versions of undelete software.  I don't mind paying for software, but I want to know that the file recovered will be playable.

Vofas Posted at 6-29 21:23
I suspect that the reason is still not in Mavic. To eliminate this in the future, try changing the SD card. Good luck

How is changing the SD card going to fix the problem I described?

How can I recover the video file that was being recorded?  The log file from the flight shows recording start and recording end, followed by several minutes of flight before a normal shutdown.

What about the huge .7z compressed file that I described?  Is this a version of the video file?  How can I recover it?

MAPilot Posted at 7-6 17:46
How is changing the SD card going to fix the problem I described?

How can I recover the video file that was being recorded?  The log file from the flight shows recording start and recording end, followed by several minutes of flight before a normal shutdown.

I just assumed that the reason for what happened is the SD card. To exclude a repetition of the situation in the future, I proposed the option of replacing the card. Moreover, if the card is faulty and the file structure is violated, it is unlikely that it will help. Try, there are a lot of recovery programs on the Internet. Good luck

So;  The first thing you want to try on MP4 files you found, is to repair the files;  which is a pain and there is several ways, and sometimes one of them works:https://forum.dji.com/thread-185097-1-1.html

Lots of tips in there you can try, make a copy of the file, before you run tools against it.  if the file has real data in it, the copy will be fine.  if the file is not playable, but has a file size thats approx correct, you have a chance at fixing the MP4 container and getting most of the video back;

What interests me if that the drone will save files in parts, and even if one file is damaged for some reason, its almost never more than the active last file that was open while it was saving video.  The DJI system breaks down and closes files after a certain file size, which can be 5 min of video or 15 min of video depending on how your recording.  All of this to say, its very strange that all of the files you were looking for are gone,  its not unheard of to have the last file of set get damaged, but almost never all of them.

I would ask, did you happen to buy this SD card on EBAY or Amazon?  there is a huge amount of fake SD cards  outs there that have a a modified microcode that self reports the card as larger than it really is.  One of two things happen with these cards, it reports an error when it runs out of real space to write to, or the SD card starts to overright itself.  This will  leave what looks like a deleted file that some tools pick up, but the file is useless as new data is written over the actualy data.

Not sure what is going on in your case - its really strange....    once you copy the files off the SD card, trying to do a file repair with software that specificalt is designed to correct MP4 container issues is your best best if not a bad SD card.  Once the data files are removed of the SD card, look for software to test the SD card;
https://photographylife.com/fake-memory-cards#:~:text=In%20my%20opinion%2C%20H2Testw%20is,F3X%20is%20the%20GUI%20version).

on EVERY SD card I buy, regaurdless of source, I run the test on it.  I have had local [retailer] purchased cards turn out as fake as the fake cards were sold to [local retailer] at some point.  This test will at least rule that out for you, and the above tip will give you a fighting chance at getting that video back.

As for reasons, turning off the drone, before it has a chance to close that file causes unplayable files.  MP4 files are very easy to damage, thus why peopel switch over to MKV files (not available on DJI) as they are better for this sort of recording, and then covert the MKV files to MP4 after recording stops.   the fix for this can be as easy as turnign on the drone and let it sit for 5 min while it closes the file, but that process is not an option for you (unless the giant zip file is the raw data the drone uses to close files? I dont know what that is however).

These are the only two things I can think would help you out.  I have had the currupt file issue a few times myself, and have in 100% of the cases been able to recover them with FFMPEG (Directions on its use pasted below)... I cant recall where I downloaded it from, but it was free so if you cant find it, PM me and I will zip a file for you to try out...  your chances of success I wonder about as the files you have were delete recovered files...  but worth a try, this process is easy:

Place the BAD video and GOOD video in the same directory as this software

Run the recover_mp4.exe tool against the GOOD video file with the --analyze switch

        recover_mp4 good.mp4 --analyze

This will spit out the command line to use with ffmpeg.exe to correct the video, there is two commands lines it will provide:

        now run the following command to start recovering:
        recover_mp4.exe corrupted_file result.h264 --noaudio --dji.avc

        Then use ffmpeg to mux the final file:
        ffmpeg.exe -r 30000/1001 -i result.h264 -c:v copy result.mp4

Once this is done it creates a file called result.mp4 that can be played normaly.

Good luck!

The DFS folder is probably part of the flight simulator that was embedded in earlier versions DJI Go app. Clearly a 7z file won't contain the video you want. I'm pretty sure that it is not the Mavic's fault, but for your help I'll mention reasons that may have leaded to an SD card corruption
a) FAT32 format has a 4G max file limit, better use exFAT
b) If the card isn't fast enough for the video recorded then you're in trouble
c) An SD card has limited write cycles and the heat the MA produces in no good friend either
d) Never unplug the SD card while the MA is on
e) Cheap SD cards contain bad sectors even when brand new (and there are fake ones that report even wrong capacity as FanOfFlight mentioned )

What type of SD card did you use?

Neo Supreme Posted at 7-7 02:54
What type of SD card did you use?

The card is a 64G SanDisk Extreme PRO microSDXC Memory Card up to 100 MB/s, Class 10, U3, V30, A1 purchased in March 2018 from Amazon.com.  It has never used anywhere other than this MA, and has served me with no problems.  The filesystem is exFAT.

It was described on the Amazon page as "Ships from and sold by MemoryMarket".  It had 4.5 stars based on 1800+ ratings, so I think it's not likely that they were fakes

heliaetus Posted at 7-6 23:00
The DFS folder is probably part of the flight simulator that was embedded in earlier versions DJI Go app. Clearly a 7z file won't contain the video you want. I'm pretty sure that it is not the Mavic's fault, but for your help I'll mention reasons that may have leaded to an SD card corruption
a) FAT32 format has a 4G max file limit, better use exFAT
b) If the card isn't fast enough for the video recorded then you're in trouble

OK, but why would a flight sim file be written to an SD card??  I've never heard that the flight sim DJI provides as a part of GO4 requires an SD card to be inserted to run.

a.  Windows Explorer reports the card as using exFAT, so that's good

b.  It's a 64G SanDisk Extreme PRO microSDXC Memory Card, rated up to 100 MB/s, Class 10, U3, V30, A1, which easily meets the requirements for the Mavic Air, so it's OK there.

c.  I don't know how many write cycles have been used, but for an estimate, I've copied everything that was ever recorded to this SD card, into a NAS and the total amount of data there is currently at 281GB across 1435 files - including plenty of multi GB video files.  That would lead me to say that there have been an average of 5 writes (I know that's not exactly true), is a very low number of writes, relative to the card size.  Also, the card is not reporting any errors.

d.  I don't think I've ever unplugged the SD card when the MA was ON.  Certainly, I never removed it while video was being recorded.  In this case, the video was shot on the first half of the flight, there were several minutes before the drone landed and the drone turned OFF.  The card wasn't removed until I got home, which was well over an hour.

e. I think SanDisk is a top tier card, and the customer rating was very good - 4.5/5.0.

Vofas Posted at 7-6 21:16
I just assumed that the reason for what happened is the SD card. To exclude a repetition of the situation in the future, I proposed the option of replacing the card. Moreover, if the card is faulty and the file structure is violated, it is unlikely that it will help. Try, there are a lot of recovery programs on the Internet. Good luck

Thanks for your suggestion.

My experience with undelete programs is that the free ones recover only smaller files or a limited number of files.  I don't mind paying for a good program but I've done so in the past only to find that the huge video file which the freeware version reported as "excellent chance of recovery" was recovered by the paid version, but was not playable.

There are a lot of such programs, but I haven't seen any comparison, to determine which ones are good.

FanOfFlight Posted at 7-6 21:51
So;  The first thing you want to try on MP4 files you found, is to repair the files;  which is a pain and there is several ways, and sometimes one of them works:https://forum.dji.com/thread-185097-1-1.html

Lots of tips in there you can try, make a copy of the file, before you run tools against it.  if the file has real data in it, the copy will be fine.  if the file is not playable, but has a file size thats approx correct, you have a chance at fixing the MP4 container and getting most of the video back;

WOW!  That's a lot to digest...I've started working on it.

A few notes in the meantime...

I've found THM files on the SD card for DJI_0506, DJI_0507, and DJI_0508, but no corresponding MP4 files.  This suggests that the MP4 files must have been created??  Aren't THM the "telemetry" files associated with videos?  Their time stamps look right on the money.

I put the microSD card back into the Mavic Air, and powered up.  Took the RC and started recording a video, ran a few seconds, and stopped.  All this time, I had the MA connected via USB to my Windows laptop.  I saw that DJI_511 was recorded, and did play normally.  Don't know what happened to the numbers between 505, the last file that I have, and 511.  There was also a 511 THM file.  

Is there any record in any file (log?), that could give a hint if, in fact, there ever were DJI_0506, 507 or 508 MP4 files created?  Isn't it odd that THM files were written, but corresponding MP4 was not????

When I connected the PC and Mavic Air via USB, I got the following message:  

Error checking (DJI-MAVIAIR(F)
Repair this drive
We found errors on this drive.  To prevent data loss, repair this drive now.
---> Repair drive
You won't be able to use the drive while Windows finds and repairs any errors.  This might take a while, and you might need to restart your computer

I cancelled because I wasn't sure what it was going to do.  The drive letter represents internal storage in the MA, and somehow I'm not sure my PC should be doing any writing to storage controlled by the Mavic Air.  Any opinions?  I've seen this before on occasion, and have ignored it.

The main reasons for"We found errors on this drive" is file system corruption due to developing bad sectors (especially in the FAT area), improper removal , virus infection, etc.  The fact is I don't think you can recover the file with an undelete program (undelete as the word implies is for files that were deleted which isn't your case). If there's a file then the chain of sectors of its content is probably broken and needs specialized technicians to recover the file with forensic methods

MAPilot Posted at 7-7 13:47
WOW!  That's a lot to digest...I've started working on it.

A few notes in the meantime...

Well. If your seeing THM files, that means the MP4 files were created also.   Based on you feedback that you have used this card for years and a approx 5 times full write that sd card is not likely to fake.  However at the end of this, test the card before you use it again just in case it has bad sectors or something else.

In the mean time if you have not found any MP4 files you have nothing to try and repair.   You chances of getting that video back is low

However.  Did you pull the videos off your phone assuming you had it set to cache the files on your phone for when you fly. I can’t recall if that’s a default hopefully you have it set to cache your flight videos.  If so that video will be the same quality as what you saw on the screen while flying.  No where near the quality on the as card but based on the effort your putting in it would be better than nothing.

Not sure if you have thought to pull the video cache files from the device you fly with.

MAPilot Posted at 7-7 13:47
WOW!  That's a lot to digest...I've started working on it.

A few notes in the meantime...

Well. If your seeing THM files, that means the MP4 files were created also.   Based on you feedback that you have used this card for years and a approx 5 times full write that sd card is not likely to fake.  However at the end of this, test the card before you use it again just in case it has bad sectors or something else.

In the mean time if you have not found any MP4 files you have nothing to try and repair.   You chances of getting that video back is low

However.  Did you pull the videos off your phone assuming you had it set to cache the files on your phone for when you fly. I can’t recall if that’s a default hopefully you have it set to cache your flight videos.  If so that video will be the same quality as what you saw on the screen while flying.  No where near the quality on the as card but based on the effort your putting in it would be better than nothing.

Not sure if you have thought to pull the video cache files from the device you fly with.

heliaetus Posted at 7-7 21:06
The main reasons for"We found errors on this drive" is file system corruption due to developing bad sectors (especially in the FAT area), improper removal , virus infection, etc.  The fact is I don't think you can recover the file with an undelete program (undelete as the word implies is for files that were deleted which isn't your case). If there's a file then the chain of sectors of its content is probably broken and needs specialized technicians to recover the file with forensic methods

Please note that the "we found errors..." message came in regard to the 8 GB internal memory!   Should I let Windows fix the errors on internal memory? If not, what should I do about it, if anything?

If you forget about recovering the video you can start by checking the card with h2testw to see what it reports. You may save then any usable data and format the sdcard; I suggest a full format using Windows or even better sdcard formatter. Then to be on the safe side check for bad sectors with mhdd because you may need to buy a new sdcard.

FanOfFlight Posted at 7-7 21:37
Well. If your seeing THM files, that means the MP4 files were created also.   Based on you feedback that you have used this card for years and a approx 5 times full write that sd card is not likely to fake.  However at the end of this, test the card before you use it again just in case it has bad sectors or something else.

In the mean time if you have not found any MP4 files you have nothing to try and repair.   You chances of getting that video back is low

I most certainly intend to run the SD card test software after this is all over.  The only reason I haven't done so yet, is that we still don't know what happened here, and that card is the only thing that might hold the key.

Think about this: the DJI software is controlling all aspects of taking the video. The txt data file shows the video record start and stop, and the THM files' existence proves that MP4 files were created. Yet, neither those files, nor any intermediate files are to be found.

These facts suggest that either

• the DJI MA software had an error, or
• the Sandisk SD card had a failure
  

But, if the card had bad sectors, what are the chances that there were 3 write failures in a row?
Also, if the SD card had write failures, wouldn't you expect the DJI software to capture the write failures?
The fact that I was able to succesfully record and play a video with that same SD card just yesterday, suggest that the card did not fail?


While I certainly apreciate everyone's input, how can we get this case in front of DJI software engineers? I thought they monitored the forums.

As to your video cache comments, FanOfFlight, I have the caching turned off, to save battery power. Also, it would be redundant, since i run screen recording on my iPhone 8, for every flight, from start to finish.

BTW: I looked at the flight data txt file, using CSView with camera related parameters:
It  apears to show the period of video recording at the begining, followed  by panorama shots. How could data recording start and end "normally",  yet there is apparently no video file?

heliaetus Posted at 7-8 09:38
If you forget about recovering the video you can start by checking the card with h2testw to see what it reports. You may save then any usable data and format the sdcard; I suggest a full format using Windows or even better sdcard formatter. Then to be on the safe side check for bad sectors with mhdd because you may need to buy a new sdcard.

Still not ready to throw in the towel.I really want to get to the bottom of this.  
I don't think the card is bad, but certainly want to thoroughly test it before trusting it again.

MAPilot Posted at 7-8 10:54
Still not ready to throw in the towel.I really want to get to the bottom of this.  
I don't think the card is bad, but certainly want to thoroughly test it before trusting it again.

Sure, I dig that, but you oughta check another sdcard with the MA to eliminate (or maybe to my surprise prove) MA's fault

MAPilot Posted at 7-7 07:24
The card is a 64G SanDisk Extreme PRO microSDXC Memory Card up to 100 MB/s, Class 10, U3, V30, A1 purchased in March 2018 from Amazon.com.  It has never used anywhere other than this MA, and has served me with no problems.  The filesystem is exFAT.

It was described on the Amazon page as "Ships from and sold by MemoryMarket".  It had 4.5 stars based on 1800+ ratings, so I think it's not likely that they were fakes

Well you definitely have the right one for the job.  Given the other responses, I would also check another SD card or two to make sure it's not the drone, though I don't believe that it is.

I understand recuva and diskdrill recovered file won't open or play . Have you tried Stellar Photo Recovery software?  becuase it's recover and repair mp4 files from drone camera. I thinK you must try at once.

Neo Supreme Posted at 7-9 02:39
Well you definitely have the right one for the job.  Given the other responses, I would also check another SD card or two to make sure it's not the drone, though I don't believe that it is.

I got a new card from BestBuy, the same card, but only 32G, and will put the card through all the tests.

However, I still have the question: what will a new card prove?
Remember that I turned my MA on, and shot a short video that recorded and played back normally, so the MA is functioning normally...but

THERE IS NO RESOLUTION OF WHAT HAPPENED TO THE MP4 FILES!!
I HAVE CORRESPONDING THM FILES WITH CORRECT DATE/TIME STAMPS AND SCREEN VIDEO SHOWING RECORDING IN PROGRESS!

What is to prevent this from happening again? I have screen video@720p, but it’s no substitute for onboard recording @4K!

JasonWilli Posted at 7-10 00:35
I understand recuva and diskdrill recovered file won't open or play . Have you tried Stellar Photo Recovery software?  becuase it's recover and repair mp4 files from drone camera. I thinK you must try at once.

The ones that were recovered, were ones I deleted earlier in June, after copying over to my NAS. These are NOT the files from the day in question.The problem I appear to have is that the MP4 files were never created in the first place, even though corrresponding THM files -were- created and are still on the SD...they were never deleted.

I haven't tried Stellar Photo Recovery - it's a subscription service, and a rather expensive one at that. I don't believe they have a free trial version.  No recovery program is going to help, if the file was never written in the first place

Vofas Posted at 7-6 21:16
I just assumed that the reason for what happened is the SD card. To exclude a repetition of the situation in the future, I proposed the option of replacing the card. Moreover, if the card is faulty and the file structure is violated, it is unlikely that it will help. Try, there are a lot of recovery programs on the Internet. Good luck

It may be that a new card install will result in trouble-free operation in the future, but there is no assurance that will be the case. Recall that the current card worked fine for about 2 yrs, and appears to work fine at present.

There has been very strange behavior, and it is currently unexplained!  Until it is, the drone is not reliable, and there is no way to make it so. I’m very disappointed, frankly, that nobody from DJI has chimed in.

MAPilot Posted at 7-12 08:03
It may be that a new card install will result in trouble-free operation in the future, but there is no assurance that will be the case. Recall that the current card worked fine for about 2 yrs, and appears to work fine at present.

There has been very strange behavior, and it is currently unexplained!  Until it is, the drone is not reliable, and there is no way to make it so. I’m very disappointed, frankly, that nobody from DJI has chimed in.

In fact, a computer is working inside the drone, but 100% of reliable computers are not. And there is always the likelihood of a malfunction of his work, which is observed when any electronic devices work.

MAPilot Posted at 7-12 06:13
I got a new card from BestBuy, the same card, but only 32G, and will put the card through all the tests.

However, I still have the question: what will a new card prove?

It'll prove that it isn't MA's fault. Some new sdcards have built in error correction code and most of them mark bad sectors. The problem is that exfat uses only one FAT and if a bad sector develops there it's unrecoverable unless you have error correction. As you can see in wikipedia there's also texfat format but isn't supported by DJI yet.

MAPilot Posted at 7-12 06:13
I got a new card from BestBuy, the same card, but only 32G, and will put the card through all the tests.

However, I still have the question: what will a new card prove?

It'll prove that it isn't MA's fault. Some new sdcards have built in error correction code and most of them mark bad sectors. The problem is that exfat uses only one FAT and if a bad sector develops there it's unrecoverable unless you have error correction. As you can see in wikipedia there's also texfat format but isn't supported by DJI yet.

Vofas Posted at 7-12 21:14
In fact, a computer is working inside the drone, but 100% of reliable computers are not. And there is always the likelihood of a malfunction of his work, which is observed when any electronic devices work.

Please rephrase...I don’t understand your point.

Yes, there is a computer inside the drone, and it does control the read/write process. It’s been a long time since I’ve written software, but I remember the need to not just command a write to media, but also to confirm that it was done successfully.  Clearly, that didn’t happen in this case, though now it does.

It would be irresponsible to assume that the DJI software is NOT the culprit. In fact, I think it’s the most likely cause.

heliaetus Posted at 7-13 02:15
It'll prove that it isn't MA's fault. Some new sdcards have built in error correction code and most of them mark bad sectors. The problem is that exfat uses only one FAT and if a bad sector develops there it's unrecoverable unless you have error correction. As you can see in wikipedia there's also texfat format but isn't supported by DJI yet.

How would a working, new, SD card would prove it isn’t the MA’s fault. It would prove that the new card works, at that time, but so does the original card! Just the other day, I powered up and shot a short video, which recorded and played back normally.

Remember that both cards are the same make/model, only different size. There is nothing to suggest that the original card itself is defective.

MAPilot Posted at 7-13 04:22
Please rephrase...I don’t understand your point.

Yes, there is a computer inside the drone, and it does control the read/write process. It’s been a long time since I’ve written software, but I remember the need to not just command a write to media, but also to confirm that it was done successfully.  Clearly, that didn’t happen in this case, though now it does.

The software either works or not. Did your drone work normally for a while? And if the suture described by you was single, it is logical to assume that this was the result of an accidental computer failure, from which not a single computer is insured. To eliminate this, fault-tolerant computing systems are used, but this is a completely different price range.

MAPilot Posted at 7-13 04:22
Please rephrase...I don’t understand your point.

Yes, there is a computer inside the drone, and it does control the read/write process. It’s been a long time since I’ve written software, but I remember the need to not just command a write to media, but also to confirm that it was done successfully.  Clearly, that didn’t happen in this case, though now it does.

The software either works or not. Did your drone work normally for a while? And if the suture described by you was single, it is logical to assume that this was the result of an accidental computer failure, from which not a single computer is insured. To eliminate this, fault-tolerant computing systems are used, but this is a completely different price range.

Vofas Posted at 7-13 05:14
The software either works or not. Did your drone work normally for a while? And if the suture described by you was single, it is logical to assume that this was the result of an accidental computer failure, from which not a single computer is insured. To eliminate this, fault-tolerant computing systems are used, but this is a completely different price range.

So essentially you're suggesting that this was just one of those things that can happen, since computers' performance is not 100% - Is that correct?

When I think of fault tolerant systems, I think of redundant hardware, and software to handle fault detection and switchover, for example.

While I do NOT expect redundancy at this price point, I DO expect that software will record and report faults of consequence.  I don't think it's unreasonable to expect the DJI system software to confirm that a write operation has been successful, and not just assume it was.  


Doesn't the DJI software create the MP4 files, and the corresponding THM files?  The THM files are on the SD...the MP4 files are NOT.  The log file doesn't contain any indication of a write failure, AFAIK. The RC screen recording shows the start and end of the video recording, just like it did in the 100+ other videos I've shot with this drone, and this SD card, over the past 2+ yrs.

If DJI wants to improve their software, and I assume they do, I would think they'd want to review their SW design and how it handles SD write failures.  I also find it interesting that there are no intermediate files on the SD card, or internal memory.

MAPilot Posted at 7-13 04:36
How would a working, new, SD card would prove it isn’t the MA’s fault. It would prove that the new card works, at that time, but so does the original card! Just the other day, I powered up and shot a short video, which recorded and played back normally.

Remember that both cards are the same make/model, only different size. There is nothing to suggest that the original card itself is defective.

I believe that the probability of MA's fault is inconsiderable in respect to the probability of sdcard's fault. Of course noone can be a 100% sure but at the risk of repeating myself it's impossible to know if the sdcard has bad sectors without fully formatting it. Windows asking to repair it is an indication that it may have bad sectors, which get marked as you use the card and so it appears to work again.
Here's and SD card that supports error correction and protects you from data loss, albeit a bit slow

heliaetus Posted at 7-13 06:16
I believe that the probability of MA's fault is inconsiderable in respect to the probability of sdcard's fault. Of course noone can be a 100% sure but at the risk of repeating myself it's impossible to know if the sdcard has bad sectors without fully formatting it. Windows asking to repair it is an indication that it may have bad sectors, which get marked as you use the card and so it appears to work again.
Here's and SD card that supports error correction and protects you from data loss, albeit a bit slow

Sorry that we're mis-communicating.
Windows asking to repair was associated with the 8G of internal memory, and NOT the SD card.  There has been NO error indication of any kind with this SD card, either reading or writing.

Even if my problem of the missing MP4 files -IS- caused by the SD card, then there is still a problem with the DJI software, because it did NOT record/display any indication of an error in writing the file.  I'm not expecting DJI software to correct all errors, but at least indicate that there was an error.  At least, I'd know that there was a problem with the video I shot, and I could immediately re-shoot it.   How can it be that DJI software would continue without confirming that a write was successful?

MAPilot Posted at 7-13 07:32
Sorry that we're mis-communicating.
Windows asking to repair was associated with the 8G of internal memory, and NOT the SD card.  There has been NO error indication of any kind with this SD card, either reading or writing.

It isn't as simple as you may think to provide the level of protection you ask, because these file operations occur at a very low operating system level, and DJI doesn't write the operating system it only uses it. This is why I pointed out earlier the texfat file system, which can help a drone detect and prevent such errors (at the cost of implementation resources), but it isn't widespread yet (and especially on removable media).

MAPilot Posted at 7-12 06:13
I got a new card from BestBuy, the same card, but only 32G, and will put the card through all the tests.

However, I still have the question: what will a new card prove?

I'm going off of my experience with SD cards and HD/HEVC video/photography.  Usually, something about the SD card was not working properly.  Could be the formatting, could be the card itself malfunctioning.  Yeah it could be something with the drone itself, though it usually had something to do with the card.  I had this issue with cell phones, GoPro's and drones.

Neo Supreme Posted at 7-15 03:25
I'm going off of my experience with SD cards and HD/HEVC video/photography.  Usually, something about the SD card was not working properly.  Could be the formatting, could be the card itself malfunctioning.  Yeah it could be something with the drone itself, though it usually had something to do with the card.  I had this issue with cell phones, GoPro's and drones.

Can you elaborate on the “issue “ you had with these devices.

I understand that writes to any media may fail for a variety of reasons, and sometimes they can’t be explained.  My question really has to do with why there’s no record of a write fail.

Some commenters suggest that the DJI software has no way of knowing if a write command was successful or not, is that true?

Isn’t there a standard that describes the interface between the SD card and the device using it?

Both the 64G and 32G Cards are formatted to exFAT.
Should they be formatted in some other way, or in some other devices?