yeah happens sometimes , I guess a little dust or dirt and stuck ! I squirt a little wd40 and gently pry off the motor mount to the back of the pinion doing one pry and next directly across from the prior ,don't want to get it cockeyed. Mine always come off with two or three pries on each side with no damage that I know of. Go slow be patient.
Seems like we are both having same type of problems, are you using loctite? I think I m going take every thing apart clean it good and rough up the mating surfaces with a little sandpaper and loctite really good. I 've gone through 3 pinions and 1 spur gear in 2 days with less than 1 hour actual run time running 6s is really hard on the whole vehicle but the fun makes it worth it
