Quad Crash , need help to analyze

ArduCopter Copter 4.4
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1

Hi, Need help finding out why the quad crashed . This quad has been flying properly for a long time, but during a testing it suddenly crashed . I went through the logs and i think there is a mechanical failure but i need help in understanding if its ESC, motor or props that caused the issue or anything else. After the crash we tested the esc and motors separately on bench and they seem to work fine .

Log file - crash log - Google Drive

2

Some problem with Motor4 - it was commanded to maximum and stayed there, indicating it didnt recover. So maybe not a simple desync, more of an actual failure. Battery voltage rises sharply when that ESC stops working, so probably just change the ESC to be sure.
Also check the low voltage cutoff setting in those ESCs and disable it or set as low as possible.