I would appreciate if someone can tell me what went wrong. We had a successfuly waypoint test last week. On Monday, we did another test at higher altitude, 200 m, and longer distance on Align's flying field at riverbank. The flight was normal at first but shortly after switching to auto mode, a military helicopter flew nearby - at much higher altitude off course. Somehow, the MP screen showed the quad changed from auto mode to loiter mode by itself, then it descended straight down slowly but steadily (still in loiter mode as shown on MP). I tried to switch to RTL, then loiter, then stable, neither was working. I couldn't take the control back. The quad continued to go down steadily, and eventually into water.
I attached the tlog here. At first I thought it's GPS failure because of the military helicopter but GPS seemed to be OK. Battery was almost full before takeoff and it's still a new battery. So it's not battery failsafe either. I don't understand why the quad went down when MP show it's in loiter mode. Also, why I couldn't switch to RTL or stable mode?