Copter ignoring Pitch command Copter-4.3.6

Hi guys,
We are using ArduCopter 4.3.6, recently we have 2 crashes because of copter ignoring Pilot input in loiter mode, we tried to find the issue maybe its ACCEL, but unable to conclude anything.
Please look into these log file.
Crash log

In log the second log:

Motors 3 and 5 are commanded to near maximum and motors 4 and 6 are commanded to near minimum to compensate for lack of thrust from 3 and 5.

In the first log, it is almost identical, except motors 1 and 2 are a bit more involved but only for attempting attitude control. It’s still motors 3 and 5 being commanded to near maximum and 4 and 6 to near minimum.
We would assume because of some loss of thrust due to prop not locked to motor shaft or motor/ESC desync.

In each log you’ve have previous flights where this was not an issue, so maybe heat is playing a role.

Vibrations do increase noticeably right at the point where attitude control starts to deviate, so there could be a physical issue, although desync could also cause non-standard vibrations.
The vibrations do increase more as attitude control and altitude is further lost, then of course with the crash, but I’m not saying those phases are related to the initial cause.

Hi @xfacta, the difference in motor output is after crash, before crash it is quite following the desire value. There is no thrust loss, actually drone hit the building.

OK, I see - so what you mean is the section where pitch input has not affect to attitude
The green line is pitch input, and you can see in previous times it had a suitable effect on attitude

There is also this bit where there is no pitch input but there is a pitch attitude change

I’m hoping the crash damage wasnt too bad :frowning:

Can you disable the proximity sensor and see if there’s any similar behaviour.
I can see there’s some inconsistency in the position controller desired acceleration, but I’m not sure where it’s coming from.

The thing I notice is the motor outputs are diverging more over time, as if heat or something is still playing a role.

I’d like to see you connect to MissionPlanner / Setup / Mandatory / Initial Parameters
and put in your prop size and battery cells, Calculate and accept any changes.
This should fix up some filter values and more importantly MOT_BAT_VOLT values.
Ensure you have these set too:
None of that is going to fix the issue, but it will help for attitude tuning and interpreting subsequent data.