20 inch hexa crash after rc failsafe triggered

hello to all,
We were flying a 20 inch hexa on auto, after reaching the last waypoint. rc faisafe triggered , then the drone just felt from the sky. the drone is built with a pixhawk cube. here2 gps, power is supplied via the regular cube power brick, ESC are x-rotor 80A and motor are custom made by the company from which we purchased it.
After looking at the logs, before the rc faisafe, everything looked alright except some higher than normal level of vibration on the z axis. we flew a lot with this drone, and I doubt the crash was caused by the vibration.
the rc used is a futaba 920mhz with the fmt-04 which is reliable and help us solve our long range issue we have with the weird japanese radio law frequency.
If anyone can help with analyzing the logs , that will be much appreciated:

thanks a lot

Your current sensor is not set correctly, that would be handy in these situations.
It looks like you’ve done a bit of manual tuning but no Autotune - that’s not a crime :slight_smile: but Autotune certainly helps.
You should connect to MissionPlanner and press Alt A and follow that wizard through with you prop size and battery type, accept all it offers.
And set this BATT_FS_CRT_ACT,1

The actual problem doesnt seem related to the RTL or radio failsafe except by coincidence - it looks like Motor 3 needed to be commanded to higher and higher output, then maximum, as it lost effectiveness. The tuning and output of other motors meant the flight controller was unable to maintain stability.

xfacta, always there to help. looks like something happened with the motor a little bit before radio faisafe. will look into that.
much appreciated,