Plane loose throttle during Auto mission

Plane version 3.2.3
During Auto mission for unknown reason the RCout of Ch 3 - throttle moved throttle to zero. The plane lost alt until it reached the ground. Activating RTL from ground station did not work.

Any suggestions what caused the throttle to go down to zero?

The log file can be downloaded from here:

I didn’t load the log, but if you have verified that indeed RCout was 0 and not that your ESC failed or disarmed, maybe ardupilot disarmed in flight or rebooted? (neither is supposed to happen, but who knows?)
If not, no idea, sorry