[Help] VTOL plane crash


We are testing the Y4 type VTOL by adding one rear motor in Tricopter.
We had a crash while conducting the hovering test in QLOITER mode.
At first, the roll, yaw, and pitch control were good.
However, the aircraft crashed as it suddenly heard the motor turn off.

and And when I did log analysis,
Just before the crash, motor1 and motor2 signals bounced in reverse, followed by a pilot signal.

We uses 12S by connecting two 6S batteries in series.
Before the test, only one 6S battery was removed and plugged in due to an EMI error.
Can this be a problem?

I don’t know what the cause is. Please help me.

Here’s the flight log.
Thank you very much for your help.


Um… I use it to help others in the future.

The problem was simply the disconnection of the ESC Signal wire.
It was confirmed that a disconnection occurred in the ESC of Motor2, which caused it to crash while tilting in the direction of Motor2.