Arducopter Crash, motor suddenly stop when tuning PID

[KevinLu]

Hi All!!
I recently have built a Quadcopter, and was tuning the PID with a slider using RC6 opt set in Extended Tuning page (In Stabilize Mode). Things were doing all right for about 10-20 min, but on my way tuning the rate roll P, the motors suddenly stop somehow. And the copter crashed. Luckily it was in relatively low height, and the copter seemed ok.

Here is the bin file of that flight.
https://drive.google.com/file/d/1WgTNkNsVHrureIm5W4yAne3sVLqjVXVo/view?usp=sharing

Help will be very very appreciated .

Thanks

[Allister (Allister Schreiber)]

Quick guess would be failure of the #2 motor/ESC.