Here is your ulog uploaded to the PX4 Flight Review.
Looking at the full parameters you have no kill switch but you do have an arming switch configured.
Watching that channel in QGroundControl with the tlog I see it used between flights but not activated near the end. The throttle increases while the servo outputs are falling so it doesn’t seem to be an RC glitch, though the reported RSSI did look a bit low during the flight. I can’t seem to confirm or deny the explanations offered so far.