AHR2 and ATT Pitch not matching up

Hi everyone!

I had a few scary flights yesterday. I flew with a proven airframe, maiden for the plane, with calm winds and almost crashed it. Unfortunately I did this with multiple planes with about the same success. All planes used Arduplane 4.5.3 with Cube Orange+ and Holybro Mirco M10 GPS. I did Accel calibration indoors and then compass calibration right before the flight.

20 seconds after launch, flying FBWA, while I was flying at a high speed and still demanding pitch up/climb, the plane pitched down and started to rapidly descend (almost 10m/s, max allowed 5m/s). Looking at the telemetry, the plane reported to be at it’s max pitch up which already visually was not the case.

Looking at the logs, at one point the AHR2 and ATT pitch estimates differed 30 degrees from each other - ATT was at 19,9 deg and AHR2 (visually in the ballpark) -10,9deg. The two logged Roll’s had a big difference at the same time as well but not as critical at that moment.

While flying, the airplane started to report wind speeds of up to 38m/s, which definitely was not correct. It started this after I had to very badly save it under Manual mode and as I was already very far away from myself (not intentional, drifted away due to plane behaviour). From manual mode I switched to RTL, when it climbed to almost 300m altitude while RTL height was 100m.

After launch the EKF POS estimate moves 180deg in the wrong direction for 5 sec compared to the GPS data. Could this be down to compass calibration?

What could be the reason for the wrong ATT estimation and how could I prevent it next time?

The flight log bin file: Flight log