Lost control when return to Normal mode

Sorry for this duplicate post but I already post in Arduplane category but I did not received any suggestion, hope someone will take a look to my log and have some ideas.
I’m new to Arduplane and I’m quite poor in log analysis but I found real weird that roll attitude change so much while Des_roll was a flat line.

Mechanical Failures

Common mechanical failures include a motor or ESC failure (including ESC sync failures), the propeller slipping or coming off, etc. These appear in the log as a sudden divergence in the desired roll and pitch vs the vehicles actual roll and pitch. This discrepancy is most clearly visible in the dataflash logs by graphing the ATT message’s Roll-In vs Roll and Pitch-In vs Pitch and to a lesser extent in the NavYaw vs Yaw. (Copied)

Thanks for your reply.

The point is that the plane was recovered from total lost of control and imminent crash when switched again to FBWA mode and after land safely.
So there was no mechanical failure IMO.

The Des_roll is flat because the autopilot does not control the flight in Manual Mode. In other modes, as you can see in your graph as well, both roll ad des_roll change according to the desired flight behaviour.

Can you tell more about your crash? It seems strange

ok for Des_roll , noted, thanks !

It happens twice the same day, once from FBWA to Manual and the other time from Autotune to Manual.
The second time I was able to recover while the first time I crash.

The plane took off in Manual mode and flew well, then it was switched in Autotune and flew well but since it was difficult to make tight turns because of ailerons small servo throw I decide to land and switch to Manual mode while the plane was flying leveled .
When I lost control I was at 50 meters, I “immediately” switch back to Autotune and the plane recover his attitude at 18 meters, after I was able to land .

I was surprised that the plane was able to recover even with a limited aileron throw and a such uncontrolled attitude losing altitude, quite impressive .