"I had the same issue with ArduPlane 2.7 on 2 different APM 2.5's. Are you by chance using the uBlox GPS? I was getting the artificial horizon start to jump around with the uBlox attached. I swapped the uBlox out for a MediaTek and the issue went…"
"I get the same behavior with my APM2 board. When I connect to the board via USB, it resets, the ABC lights come on and there is some TX activity. Then A(red) turns off and stays off. When I look at the MissionPlanner console, I see the following:…"