I got myself a pre-owned mini 2 for christmas; well impressed with it, amazing bit of kit. Only thing is it seems to have a wee habit of diving on its own seemingly randomly for no good reason. It's happened a few times now at various heights and distances, it just starts slowly descending. You can fight it but full stick up only sloooowly raises it, like its lacking power, nowhere near as hard as it should, and when you stop fighting it goes back to heading downwards. A couple of times its touched down on the ground and the props continue spinning and won't shut off  using CSC (set to emergency only) - like it doesn't know its touched down or theres anything wrong, it still thinks its hovering.  Usually sticking it into a different mode will snap it out of this behaviour and it starts flying normally again. RTH seems to sort it out too.  Is this a known issue? I've got a couple of logs I can share of flights where its happened if I can figure out how :p

First time it happened at around 30 meters away, 10 meters altitude over grass, it dropped a few meters on its own and I had to battle it and fetch it back while it struggled to maintain height. Today it happened again a couple of hundred meters away 50 meters up over a river with no down input at all.

Any help appreciated

https://www.phantomhelp.com/logviewer/8RDCRIIAP03EQ721BXQS First time it happened; Shenanigans start around the 1 minute mark.
https://www.phantomhelp.com/logviewer/11IZ1N4805QC0CPZL2DR And around the 3:45 mark here

Hi Rowan,

Interesting logs....

First log :
Flying low over water or grass ; if the bottom height sensor cannot determine correct height values it looks like it had impact on the height stability. But never seen this before like this.
See the VPS height line fluctuates between zero and 6 meter.....was the surface belew the drone level and flat or ??
Plus the baro height follows the VPS height, uh ?  if drone fly at certain height and the distance between drone<>surface got less than the baro height remains the same.

Second log:
Not normal to loose so much height.
See the blue height line coloured red where your Mini  2 dropped height with no down input.
It is 'normal'to loose some height going from forward to aft stick input, but not like this.

Cold and humid weather? icing on the blades ?

The only thing (imo) you can do is to calibrate the IMU and test fly again.

cheers
JJB

JJB* Posted at 1-1 12:07
Hi Rowan,

Interesting logs....

Thanks for getting back to me. Glad to hear its not normal, it was concerning me a bit :p Its still under warranty with mpb anyway if it turns out to be a knackerjob.

The first log was over a pretty much flat grass football pitch, second over a river. It wasn't so cold id be worried - over 5 degrees I think, and it had been raining recently so a damp-ish day. I tried calibrating the imu on the day once already and it carried on afterwards; i'll give it a go again tomorrow and make sure its done perfectly! Its done this a couple more times than just these two logs posted but i've done loads of short flights the last couple of days with just getting it and those are the only two I remember which logs they are!

I've got everything updated to the latest firmwares too.  

RowanMachine Posted at 1-1 12:19
Thanks for getting back to me. Glad to hear its not normal, it was concerning me a bit :p Its still under warranty with mpb anyway if it turns out to be a knackerjob.

The first log was over a pretty much flat grass football pitch, second over a river. It wasn't so cold id be worried - over 5 degrees I think, and it had been raining recently so a damp-ish day. I tried calibrating the imu on the day once already and it carried on afterwards; i'll give it a go again tomorrow and make sure its done perfectly! Its done this a couple more times than just these two logs posted but i've done loads of short flights the last couple of days with just getting it and those are the only two I remember which logs they are!

Oke.

Bit worried about both flights, if log1 is flown over flat grass foorbal pitch...than both height indications should be oke. if vision height is having a hard time over wet grass that the baro height should indicate level flight with no up/down input.

Flying over water can be tricky, for sure low flying over streaming water.
Should be steady height flying at 30 meters baro height.

cheers
JJB

JJB* Posted at 1-1 12:43
Oke.

Bit worried about both flights, if log1 is flown over flat grass foorbal pitch...than both height indications should be oke. if vision height is having a hard time over wet grass that the baro height should indicate level flight with no up/down input.

Hm, sounds like i'll be getting in touch with mpb when they reopen then. And they've no more in stock to replace it with, typical! Fingers crossed they've got a pile waiting to be processed that they've not gotten round to over christmas, i'll be devastated to not have it for a few days its great fun despite its suicidal tendencies :p Thanks for your quick replies!
Stuff thats worth noting: Anecdotally it usually happens shortly after I fly it fast and get the 'The flight attitude angle is larger in Sport mode. The gimbal will rotate when the aircraft starts or stops. Use Normal mode if required for stable shooting.' I'm going to try turning tips off tomorrow and see if that helps!


Also it seems to happen when i've been above the 30m mark or descended to around/below that height. Is that the range the vision sensor kicks in, so maybe its getting back to that height and swapping sensors when it should be working and the vision sensors having trouble somehow? Just guessing at possible causes... Hopefully its just a one off!

One point, if mpb ( Who are they? ) are selling these second hand in a High Street store ensure, whilst you are in the store, that the drone is not bound to the original owner's DJI account and that the controller is not bound to the drone. ONLY the original DJI account can undo these bindings. Refuse any that are bound unless the store can give you access there and then to the original DJI account and undo these bindings before you leave the shop or BETTER YET get an assistant to do it in front of you so that you can see it done.
The original DJI account MUST connect to the internet for the unbinding to be registered.
Then connect your phone to the drone and controller etc. and check that YOUR app gets no warnings concerning the equipment being bound.
It may be necessary for your app to have internet access.
NOTE this binding has to do with flyaway insurance.
It has NOTHING to do with the linking/pairing of the controller and drone for control purposes.


You will need to google this stuff.

Sean-bumble-bee Posted at 1-1 13:24
One point, if mpb ( Who are they? ) are selling these second hand in a High Street store ensure, whilst you are in the store, that the drone is not bound to the original owner's DJI account and that the controller is not bound to the drone. ONLY the original DJI account can undo these bindings. Refuse any that are bound unless the store can give you access there and then to the original DJI account and undo these bindings before you leave the shop or BETTER YET get an assistant to do it in front of you so that you can see it done.
The original DJI account MUST connect to the internet for the unbinding to be registered.
Then connect your phone to the drone and controller etc. and check that YOUR app gets no warnings concerning the equipment being bound.

Mpb are a UK based fairly reputable second hand camera company. They're usually alright for camera stuff so I took a punt

I've just checked and the drone says unbound, the controller says it's bound to the drone. Should that not be the case? I assume I'm not covered by any DJI warranties or owt anyway, it says it was first activated about 600 days ago and it's pre-owned merch.

Edit: clicked to unbind and it worked fine with no authorization. Could re bind it with my details but not sure I should if am potentially returning it!

Hmmm this binding seemingly stuff gets more and more complicated  as time goes on.

The long and short of it is that you do not want the drone to be bound to someone else's account, it is quite likely that you will be unable to fly it with your own account.
NOR do you want the controller to be bound to the drone.
'Normally' that would mean that you MUST use that controller with that drone, an alternative controller will be limited to 5 flights with that drone. It might also mean that that controller can not be used with another drone.

That binding of the account and drone relates-to/stems-from FLYaway insurance and is designed to prevent a lost-and-found-by-someone-else drone being flown by someone else, the binding of the controller and drone is a T&C condition for the insurance to be valid.

It is supposed to be that ONLY the original account used in the binding process can undo the binding.
If you do a google you will find multiple "My xyz is bound to abc, help." threads.
Once the bindings are undone by the original account and the unbindings have been registered the restrictions are lifted.

That said I was able, without care refresh or flyaway insurance, to bind a mini 2 to my account, however that binding prevented nothing. I was able to fly the drone with multiple DJI accounts and multiple controllers in any combination but, from memory, ONLY the/my original account could undo the binding.

If you, not using the original DJI account, were able to undo a binding then that is a "new one" to me.

Multiple reputable sellers of pre used or opened stuff have been caught out by this, including Amazon etc..

Sean-bumble-bee Posted at 1-1 14:14
Hmmm this binding seemingly stuff gets more and more complicated  as time goes on.

The long and short of it is that you do not want the drone to be bound to someone else's account, it is quite likely that you will be unable to fly it with your own account.

I just clicked unbind, it said are you sure, you need it for DJI refresh blah blah and I clicked yes, and it said done.

The DJI app prompted me to bind it again so I bound it to my account and now it's all showing as bound again. Figured I'd see what happened. Is any of this relevant without any DJI based insurance anyway? Could this be the cause of my suicidal drone?

RowanMachine Posted at 1-1 14:33
I just clicked unbind, it said are you sure, you need it for DJI refresh blah blah and I clicked yes, and it said done.

The DJI app prompted me to bind it again so I bound it to my account and now it's all showing as bound again. Figured I'd see what happened. Is any of this relevant without any DJI based insurance anyway? Could this be the cause of my suicidal drone?

Could this be the cause of your suicidal drone? I very much doubt it.


I think the question "what happens once the insurance lapses?" has been asked, I think the answer was "the bindings remain in effect". By implication so too do the consequences.
What happened in your case .... your guess is good as mine, maybe I boobed, I will check in the morning.
But, as I said google it and you will find numerous tails of woe.

Sean-bumble-bee Posted at 1-1 14:46
Could this be the cause of your suicidal drone? I very much doubt it.

I'll have a proper read about it and make sure I check when I get my replacement. I don't expect any bother replacing it with em if there are issues so I don't mind it for a bargain :p thanks for the heads up

Hope it resolves quickly mate!

My mini 2 had an incident last week where the elevation reading disconnected from reality and the drone attempted to correct. The elevation reading suddenly dropped from ~20ft to MINUS 500 ft and the drone went beserk, climbing automatically to about 150 feet before suffering an engine failure (presumably from the motors going crazy trying to stabilize height..) No solutions yet..

SouthAfricaGuy Posted at 1-3 00:33
Hope it resolves quickly mate!

My mini 2 had an incident last week where the elevation reading disconnected from reality and the drone attempted to correct. The elevation reading suddenly dropped from ~20ft to MINUS 500 ft and the drone went beserk, climbing automatically to about 150 feet before suffering an engine failure (presumably from the motors going crazy trying to stabilize height..) No solutions yet..

That doesn't sound good!

Am I right in thinking new firmware was released a couple of weeks ago - could this be foibles with that?

I tried flying it again yesterday but it wouldn't hold alti at all in a light breeze. Just kept on descending to the point it was touching the grounds. I'll upload a couple of logs of it and edit em into this comment in case any geniuses want a look! I've got another day to explore the problem anyway, shops not back open til tomorrow, bliddy new year!

Edit: https://www.phantomhelp.com/logviewer/39ZB93G37L277T1TTIPL - is it normal to go 800 octillion mph for a millisecond every now and again?

RowanMachine Posted at 1-3 01:05
That doesn't sound good!

Am I right in thinking new firmware was released a couple of weeks ago - could this be foibles with that?

Hi,

Don`t know in wich weather / wind this flight was flown...

But it could not hover stable at all.

With no RC inputs for Pitch forward/aft and Roll left/right it should hover at the same position.
It did not do that!  see the polar chart, yellow line is where drone moves around with no RC input.

Try to get another drone.

cheers
JJB

JJB* Posted at 1-3 01:29
Hi,

Don`t know in wich weather / wind this flight was flown...
[Image]

Yesterday was in some trees, 3 or 4 degrees celsius, dry and sunny out, light breeze. It wouldn't behave at all, and a few of the logs are showing insane speed readings here and there (I did 4 flights testing). I did recalibrate the IMU before taking off. Maybe that took badly? Definitely set on getting a replacement either way, something looks out of whack and I can't afford for it to park itself somewhere silly :p

If taking or sending the drone back, keep the flight logs for the flights you have flown with the drone, they are a useful record of not only the flights but equipment serial numbers etc. too.
I move mine to external storage.
I have seen single line instances of Warp Speed travel in a few recent logs from flights on here etc. I wouldn't be worried about them provided that they remain isolated.