The aircraft accepts a mission, begins takeoff and disarms after 2 seconds?
I am facing similar issues. My Configuration is Plane/PX4/CUAV v5. The plane spools up the motor for a few seconds. After approximately 5 seconds the aircraft motor stops and QGroundControl Station shows a message that auto-disarm has been initiated.
This happens, however, also in Manual mode with no mission activated.
According to a friend’s hint, I am going to check the power module.
Auto disarm for fixed wing vehicles doesn’t work well for some takeoff types. Try setting COM_DISARM_LAND to zero.
@Antiheavy found that also COM_DISARM_PRFLT measures the timeout between arming and takeoff. Setting COM_DISARM_PRFLT to zero solved the issue for me.