Pitch / throttle controller stop work randomly in Auto mode

I experience a crash may be due to the pitch and throttle controller randomly stop functioning. There is a similar incident happen a few months ago where my plane is out for a mission, just before reaching way point 1, about 1 KM from home, it start losing altitude and fail to navigate to way point two. As it was still within telemetry range, I manage to switch to RTL, luckily the decent rate is quite slow even without the auto pilot controlling the pitch axis, I manage to fly it back home with altitude to spare. I review the tlog and found out that just before the plane start losing altitude, the pitch and throttle controller stop working. I assume that this may be is a firmware bug and update to version 3.4. A few days ago we fly again, it has successfully completed 4 flight but during the fifth mission, it didn’t come back at schedule time and it was out of telemetry range. Anyway we are lucky that the plane actually crash land gently on a tree and it was intact. We drive to the mission site and suddenly had telemetry connection so we just walk up to the plane.
I attach the data flash log file here and hope someone can have a look if the similar problem resulting the crash. Thanks

Just found that I can not up load log file here. So here’s the link :

I don’t see any flight data in that log. Did you post the wrong one by accident?