Hardware: Matek H743 wing, all external hardware unplugged, powered via USB.
Software: ArduPlane 4.0.6
Symptoms: The bord does not complete startup. It starts as usual, red LED on, blue flashing. Then red on and green flashing with startup melody. just before the melody ends (one of the last tones) the FC hangs up: green LED stays on or off (randomly) constantly and the buzzer stays on with a constant tone or is silent without playing the last tones of the startup music. USB serial is available on windows but missionplanner throws an error upon connection.
A few weeks ago, the symptoms became apparent for the first time. I installed the 4.0.7 beta plane via missionplanner, no change. I installed the copter firmware (resetting the parameters) and the board booted again. I changed back to plane 406, set all parameters as disired and everything worked at that point. Since then I flew a couple of times (around 3 flight hours and >10 hours runtime on the ground for setting up parameters, experimenting with mavftp, scripts etc.). Today I had a moment in manual flight when the plane was uncontrollable (a watchdog reset I presume, as the GCS showed some messages conaining something like that)
After landing and some fiddling with the GCS, I powercycled the plane (maybe a few times, I do not remember exactly) and had the same symtoms as a few weeks ago. I do not feel comfortable to just reset the FC with copter firmware again and just keep flying. Maybe someone can help me finding the problem?
(At 90.2% of the telemetry log the watchdog event happend, for the bin logs, it was right at the end of 75/begin of 76)