Tertiary Vibration and crash

We have been flying this drone for quite some time now and now we observed that the tertiary vibration increased exponentially in one flight and then the drone crashed. I am not sure if that was the reason or something else. Please help me understand the issue and how do we resolve it.
Please find the log file below.


Please let me know if any other input is needed from my side.

Looks like a typical thrust loss in your case on Motor 4. Commanded to max, opposite arm Motor 3 dropped to Min to attempt stabilization and down it goes due to lack of thrust to fly.

Thank you for your response. I also observed an increase in tertiary clipping. Before the crash. A faulty powerplant and tertiary vibration are the two issues I see happening at the same time on this drone. But how are this two issues correlated ? Did one lead to another? I am not sure.

The vibrations are likely a result of the motor failure.

The vibrations are not beyond the acceptable limit as far as I can see. I can only see the tertiary clipping to be crazy. It happened well before the drone crashed. So I would like to know why we see tertiary vibration.

I don’t know but it’s coming from IMU3:

Update to 4.2.1 (you posted in the wrong thread) and make sure EKF3, not EKF2, is enabled.