I had a strange failure (right Elevator) last year and was very lucky, not to loose my Ultraflash. The reason was probably not the servo but a device between receiver and servo but later I exchanged everything including the servo. What I've learned, even with the redundancy of two elevators and two channels you have no chance, when one elevator goes fully down and stays in this position. In my case it went back to normal after a few seconds. I could reproduce the failure on ground, the servo intermittantly went to full down position.

Regards
Walter