Hi everyone...

I took the Mavic 2 Pro for a flight today, carried out the pre-flight checks, the weather was perfect for flying and I took off.  Everything was normal until a variety of warning messages came up on the screen after around 4 minutes of flying.  The drone disconnected then reconnected to the remote within seconds and then suddenly it decended from 80ft to 38ft within a few seconds whilst I was pushing the left stick upwards.  As it was rapidly descending, the front props came into view of the camera and the drone appeared to be yawing rapidly.  I managed to engange RTH and the drone returned in one piece! I managed to take a picture from the camera which shows the gimbal not level after RTH was engaged (see below).  I have been having issues with the gimbal level, and it doesn't stay completely level during flight.  

https://www.dropbox.com/s/l0fxp0ot1sr8eij/DJI_0099.JPG?dl=0

The following warning messages came up in this order:

1) Switched to Backup IMU
2) Navigation System Redundancy Switch
3) Ambient Light too Weak. Vision Positioning obstacle sensing is unavailable. Please ensure safety during the flight
4) Obstacle sensing range narrowed. Fly with caution
5) Upward Obstacle Detected (there was nothing above the drone - I was looking at it at the time)
6) Switched to Backup IMU
7) Navigation System Redundancy Switch
8) Gimbal Roll Reached Movement Limit
9) RTH

I am unsure how to attach the fight record, but I have screen-recorded the flight from the DJI Go 4 app and attached it below:

https://www.dropbox.com/s/e0gyhm4fgfw7u32/IMG_8161.TRIM.MOV?dl=0

Can anyone help me with this?  Thanks

*EDIT*

Flight Record link - https://www.phantomhelp.com/LogViewer/FRMYCKUKA2FOBAEBWZ32/

Hiya,

use this link > https://www.phantomhelp.com/LogViewer/Upload/

afterwards post the link on here.

cheers
JJB

JJB* Posted at 1-30 13:45
Hiya,

use this link > https://www.phantomhelp.com/LogViewer/Upload/

Hi JJB,

Here's the link...

https://www.phantomhelp.com/LogViewer/FRMYCKUKA2FOBAEBWZ32/

Game_Of_Drones Posted at 1-30 14:00
Hi JJB,

Here's the link...

HIya,

Had a look at your flight.

Indeed loss of height as you said. Just before that IMU 2 became active again, so there is a IMU1 fail.

After switching heading indicating 223 > 151 > 238 > 163 > 140. ; this when 70% yaw left input.
So yaw went crazy too. After that a descent to 39 feet.
See the heading purple line goes funny at 2700 ID x -axis. (lower chart)
See the speed and calc speed line goes apart, this indicates a IMU 'error'.

Guess the height signal went wrong in the control system. Looks like the RTH resets it all and drone flew back home.

Better ask DJI for assistence.

Think they will say calibrate IMU ect.

cheers
JJB

JJB* Posted at 1-30 14:41
HIya,

Had a look at your flight.

Hi JBB,

Really appreciate you having a look at this for me.  I was assuming it was an IMU error but the scary thing is 1) It happened in the first place 2) I had to issues on the IMU before the flight, and 3) if this had happened when the tide was in and I was at a lower altitude I would have no drone...

Will contact DJI support, thanks again for the help.