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.