A couple of weeks ago we were with Mike Caglia at the field when he was practicing his freestyle for the TOC.

He was hovering in front of us when suddenly the plane hopped the fence and was coming straight at our heads.
It was obvious that Mike never intended this maneuver in fact he was noticeably shaken.
When he brought the plane back into the pits he found that when his elevator Gimbel's were in the full up elevator position and some force (minimal) was applied, that the signal actually reversed and went to full down elevator with the Gimbel still in the full up elevator position.
I consider myself lucky that it was such an experienced pilot on the stick. If it were me, I would have probably panicked and who knows what could have happened.

The scenario speaks for itself.
Plane $10K Radio $1K
Pilot skill level $ Priceless

It can happen to anyone. No matter how good you are or the equipment you use