I have hundreds of flights on 7955s. In 170cc aerobatics with bad engine vibrations to many jets over 20kg with no problem .
I own more than 50 of 7955 and i had no problem all this years.
Mechanically its impossible for this servos to jump a gear IMHO.
I remember years ago i made a mistake on programming of four 7955 gang rudder setup ,and i ended burning the one was not tuned.
But the other three didnt manage to damage that ones gears.Only fight against it and burn it.
I also have a hotspot. With twin 7955 ganged up per elevon.
Do you have two elevons on each wing ? or single surface?
If you have one elevon on each wing how many servos you run on it?
What is your receiver setup? Batteries? Powerbox?
Have you opened the servo to check the gears?
my2c