Well theres your problem, someone went and took all the internals out of your mechbox!
Now in an AK, if the grip is too tight it would actually pull down on your cradle and LOWER your motor.
As for the gears, if teeth aint broken, the gears aint broke. Simple as that.
Infact there's this wonderful thing called work hardening that makes used gears more resistant to teeth breaking off lol
Now your solution is to properly adjust your motor height. Your 400fps spring should being working off an 8.4v large battery or an 8.4v stick battery with torque up gears. Put a 10A or 15A fuse in there. And of course the golden rule of how not to break your gun:
If nothing, or something that sounds bad, happens when you pull the trigger, then DONT keep pulling the trigger
