Reason for crash?

We have been flying this quadcopter for a while but recently over the past month we have had two crashes. We don’t know what the exact issue is, we don’t know if it’s the motor or the esc issue, can someone please help us troubleshoot the reason.
The drive link for the crash logs is given below,

It looks like motor 4 that is connected to RC output 5 failed.

So do you suggest that the RC output 5 is the issue? Hence RC output signals sent to the ESC of the motor 4 is unstable which caused the crash?

there is no way to tell from the log, just that that motor lost thrust. you will need to check all the usual suspects:

check propeller is tight
check the motor turns freely.
check the motor windings for any burning, will usually smell burnt if they have overheated.
check esc signal wire has not worked loose from the flight controller.
check esc power and motor wires.

what escs and motors and flight controller are you using?

We use Hobbywing X8 motors with inbuilt ESCs and Pixhawk Cube orange+