Hamm radio is suspicious. I think especially here in Alabama. FCC does not look to hard in houses in Alabama, USA. I know Hamm has FCC regs too, but I know several at a club have crashed in unison and there is a tower; near to the field; next to a trailer that worries everyone. I have lost one that was PCM...hovering...failsafe no good for that one. Intresting...sad....impressive death.
Oddly enough trains too. At least where I am and my frequency....whatever... I hear it coming and land. A signal will precede it that will throw my PCM's into failsafe. Give me a real workout with the FMs. Took me a few times to figure that out.
Place where I fly by myself mostly. 100 yards from a track on the backside. Could be the harmonics of the trains main or wheel motors, transmission signal, its a mystery that I can nip in the bud...land and wait.
I have had one servo do the extension thing too, flying...then loop, loop, loop..then level, no stick input. Never saw a problem in that new Futaba servo for the elevator. Never would do it on the table. I changed frequncies over that before I figured out the problem. My first plane. Be thankful it did it on the ground. I still fly that first trainer plane with Hitec 635's.