Hello everyone,
I'm a newbie here and I have one question regarding my Mavic Pro.
I noticed something that looks strange on the bottom shell of my Mavic Pro, and my first impression was how could it be scratched so badly.
Upon closer inspection, those were not scratches but it looks like the paint was peeling off along the edges of the shell as well as between the grooves of the heat sink.

Does anyone out there have this problem and do you know what might be a possible cause of this?  Your input is very much appreciated.

Is this a new MP??  I'm kinda curious about the scratches/marks around the screws also.  I've had mine for almost 18 months and 5.8 million feet of flight time and mine looks nothing like that.  Have you gotten it wet maybe?  Landed in wet grass maybe??

It looks so bad that you can fear what it looks like inside. To me it seems as if it has flown in a very humid and perhaps salty environment.

Something that also hits my eye and makes me wonder is why the rear sensor is covered?
It also seems that the front bottom sensor is damaged.

oh dear - that does not look good at all. As Brad says ; he and others have done considerable more milage and our drones do not and should not look like that.
It appears to me that someone has attempted to open the drone. my guess is the reason for the opening of the drone was to investigate what seems to me to be an initial over heating situation (which caused the damage to heat sync paint) -
this drone appears to have sustained some damage (excess heat is my guess ) and some one hacked it open to explore the insides.  
if the hacker did not tamper with electronics on inside and if it still flies and if it did not suffer a water landing then it may be good enough to continue flying.
watch out for error messages and if any are received go home or do not fly until resolved. good luck

Thank you all for your reply.  I bought this Mavic used and I did thoroughly checked out.  The gimbal and the 4 arms look flawless indicating that it's never been crashed.  All functions appear normal in DJI Go 4 app and no errors show up.  The Mavic flies incredibly well and stable.  The ssid and WiFi password match with the sticker on one of the arms.  However, the stickers under the battery and the one misplaced on this bottom shell are different indicating that the shells have been replaced.  I am kind of puzzled because the mavic seems to be good except the obvious problem that I saw on the bottom shell.  So it looks like overheating issue?

Bekaru MP UAV Posted at 2018-10-24 13:08
oh dear - that does not look good at all. As Brad says ; he and others have done considerable more milage and our drones do not and should not look like that.
It appears to me that someone has attempted to open the drone. my guess is the reason for the opening of the drone was to investigate what seems to me to be an initial over heating situation (which caused the damage to heat sync paint) -
this drone appears to have sustained some damage (excess heat is my guess ) and some one hacked it open to explore the insides.  

Emphasis on the ATTEMPT to open.  The Torx screws along the top edge are wallowed out.  Like someone didn't have the right size torx bit and rounded them off.  I missed fact that the Aft Sensor was covered by the sticker.   There is evidence of corrosion around all the screws.  In addition to the heat sink paint, the paint on the shell around the DJI Logo is also messed up.  

Even if it was refurbished by an authorized DJI repair facility, they would/should have done a better job of repair than this.  This looks like someone opened it up in their garage.  I'd be really cautious about this one if it was sold as a new one.  

I bought this Mavic used and I did thoroughly checked out.
No, you did not... what about the damaged sensor?

The gimbal and the 4 arms look flawless indicating that it's never been crashed.
Could all have been replaced.

So it looks like overheating issue?
I don't think so. More like corroded aluminum due to moisture.

Remove the sticker covering the back sensor - it doesn't belong there. Are you sure all sensors work as they should?
Something is wrong if there are no error messages, with that sticker sitting over the rear sensor.

And zoom in and look really close at that front OA sensor.  That looks BAD around it.  It might fly right now, but I don't think that I would trust it too much.  

It looks like you got something corrosive on your Mavic, I live by the sea always wipe my drones down after use , but after two years mine is still perfect.

I think the 2 OA sensors (2 pinhole cameras) on the bottom are fine.  I checked in the DJI assistant calibration on my PC and I see the images on both cameras.  Also during landing I tried to put something underneath the mavic and it did detect obstruction and started slowing down and hovering.

What looks weird though is that there's glass cover on only 1 of the 2 OA sensors on the bottom shell.  
Looks like the bottom shell is totally messed up for some unexplainable reason.  If that's the only problem then I can just replace the shell.  I'm so new to this and of course ignorant about the whole thing, so I'm very grateful for any help or advice you have about potential problems I should watch out for.

Yeah that's been taken apart by someone who had no clue what they was doing. My guess is they realized they messed up,quickly did their best to hide the damage and do a quick touch up and sold it to the first person that happened a long. Unfortunately, thay person was you.

I opened the bottom shell and I saw nasty corrosion inside.  Could this be from water damage or the ocean mist?  If it was water damaged before then why did it run perfectly fine with no errors?  I'm completely puzzled.

Now that you are mentioning that, when opening the bird you saw extensive corrosion inside, a possible explenation to this comes that the drone might have been involved in some kind of immersion accident, most probably fresh water since it is still running. Looks like they opened up to dry it out and avoid more damages and hey they got lucky and the drone is resilient enough that still flies even with extensive damage.

I believe you have mainly 2 options here:

- just leave it how it is and fly it until it just decides enough is enough. Which I would strongly advice against, because if something goes very wrong you could be accused of negligent flying behavior and knowingly endangering public safety.

- Take it to DJI or an authorized repair center, but what you might find will probably be very hard to swallow and a bit expensive to repair. I keep my fingers crossed for the damage to be minimal and just nasty cosmetic corrosion which could be cleaned and serviced without having to resort to extensive repairs.

Cheers!

Did you at least get a really good deal on it?

I got it for $370 but the guy didn't tell me about the problems.  I did a flight test onsite as well as checking all statuses in DJI Go 4 app and everything appeared normal.

Soon a DJI rep will log in and advise you to send it in for repair

djiuser_xzE1e37dlbPI Posted at 2018-10-24 17:14
I opened the bottom shell and I saw nasty corrosion inside.  Could this be from water damage or the ocean mist?  If it was water damaged before then why did it run perfectly fine with no errors?  I'm completely puzzled.

It seems that my guesses was right.
Don't fly it again before it has been checked by DJI - it could end up really bad.

Nicely done - thanks again for sharing.

I would go as far to even question whether that is fit for purpose (to fly safely). Looks like a massive corrosion issue.

That drone has clearly had some seriously rough treatment. Looks like corrosion damage to me. I've landed mine on sandy shores, rocky surfaces, damp grass, rough concrete - and it's still unmarked.  I fear you've been had.

I agree with other guys the damage doesn't concerns overheating issues but that drone went in touch with something of corrosive

Hi, thanks for reaching DJI Forum. We do appreciate bringing this query to us. I understand that you might be puzzled of the history of this aircraft since you mentioned that you purchased this already used. I'd like to ask, have you already contact customer support to check the history of your Mavic Pro? Let's try to review if this was sent for repairs already. We're here to help you. Thank you.

Thank you DJI Gamora, I haven't contacted customer support yet because I didn't buy it directly from DJI and I don't know if they are willing to help.  
Not sure if I can post a YouTube link here but there's at least one person in YouTube that had exactly the same problem I'm having: Nasty corrosion underneath the heat sink.

https://youtu.be/D-HBjryhp08

djiuser_xzE1e37dlbPI Posted at 2018-10-24 17:14
I opened the bottom shell and I saw nasty corrosion inside.  Could this be from water damage or the ocean mist?  If it was water damaged before then why did it run perfectly fine with no errors?  I'm completely puzzled.

Possibly because drone was found, after being outside and exposed to moisture.  Then drone was salvaged by replacing damaged parts inside.  Bottom was cleaned up, and reused.

Would explain why screws look like someone used on point of a pair of pinch nose pliers to take out screws.  With other point scratching bottom around screws.

FlyDK Posted at 2018-10-24 14:17
I bought this Mavic used and I did thoroughly checked out.
No, you did not... what about the damaged sensor?

Agree, with not thoroughly checked out.

With back sensor covered, the drone should fail Assistant-2 VPS (downward) calibration.  

Exactly why I will do without until I can buy new.

I thought I checked it thoroughly; obviously not.  Hard lesson learned.

I would send it to (an authorised dealer or) DJI, and have it completely checked. would not take the risk of my drone falling from the sky and damaging something/someone

Did you by chance fly this to the international space station and back?

I would not fly that thing in it's current condition. Corrosion on the heat sink is the least of it's problems.  If you crash that thing into someone's face you will be sued or the adult responsible for you will be sued. Either way that thing has some pretty bad issues from first glance... a reason why you got a $1k drone for $400.
You got jacked/got what you paid for?