Plane 3.5 crash - no apparent reason

My TBS Caipirinha with pixhawk has flown perfectly for more than 50 flights. I upgraded to Plane 3.5.2, recalibrated the compass and accell successfully and retuned the airframe with Autotune. The plane flew ok for 1 flight and then spiraled to the ground under power for no apparent reason. The controls didn’t work at all, although I could see in the telemetry that modes appeared to change as I tried to save the plane. the plane was a complete write-off
I have attached the telemetry and log files at the dropbox links below:

Any help would be greatly appreciated as I don’t want a repeat with my other aircraft.

Hi - that doesn’t look like the correct tlog. Despite being huge (290MB?) there is no flight in that log - all seems to be a disarmed aircraft sitting still.

Hi, sorry, seems the wrong file uploaded - here is the right one (hopefully!)