Suspectible servo broken and PX4 dead

[JohnSnowball]

Hello, here is a standard vtol, I made successful flight for about 10 times this month, however yesterday it crashed in a strange way. Here's the log:
https://logs.px4.io/plot_app?log=89a9aee2-cb5d-4451-b816-925f508ebd64
PX4FMU-V2， no modification in flight control modules from master.

All begins normally, and during mission to the third waypoint, it starts sinking with a very big negative roll angle. The after a few circles, I switched to the RTL mode, it continues to sink! Then when it starts to nose dive, I tried to turn the plane into multicopter mode, no reaction, crash. Please see the 3D replay, it could be more clear for you.

I checked log, found logger stopped when plane is still in air(start to nose dive), I guess that's why it didn't do back transition.

I got two probelems:
1. Why can't the plane reach it's desired roll angle suddenly? Is it due to a servo broken? How to confirm this point? I think it's the biggest problem that made plane sink.

2. Why PX4 is dead? I have no idea about this. Is it a hardware problem? Or stack overflow?

If you need more information, I will try my best to support you, but I can't fly this plane anymore as it's totally crashed...

[JohnSnowball]

@RomanBapst suppose you are an expert in vtol...

[mhkabir]

Possibly related : #9108

[bkueng]

@JohnSnowball do you remember if you made any parameter changes or did a calibration before the flight (without rebooting)?
Do you have a QGC telemetry log?

[JohnSnowball]

@bkueng I really did some parameter changes, but maybe no calibration as I have made about 10 flights before for the same plane. How to get that QGC telementry log?

[bkueng]

How to get that QGC telementry log?

They are stored under the 'File Save Path': https://docs.qgroundcontrol.com/en/SettingsView/General.html#miscellaneous

[LorenzMeier]

Closing: #9271 (comment)