Metal to metal contact is the prime suspect and is the most likely cause. This is often very hard to track down. ( muffler rubbing maybe?) Antennae location and mounting is the second most likely cause. Servo problem is possible, but I think it is unlikely. You will find (hopefully) the problem in metal to metal and or ant. location.

Good luck.

My Freya rarely gets hit like that but I hvae seen it. Of course,
having an incorrectly set collective failsafe (max neg pitch) doesn't help
(Hello MA, send more TuffStruts!). I've had the machine glitch
on certain days at certain fields in certainn orientations (w/ Rev. whip anten)

You might have had static discharge from the belt to the tailboom or
maybe the engine mount bolt touched the muffler. There aren't alot of
metal to metal touching possibilities on the Freya.