I replaced the idler gear inside the diffbox with a metal gear, because the original gear was missing one tooth. Out of the box.

Make sure the screw that holds the outside gear on the shaft is securely thread locked. On mine the guys who built the car in the factory (the car comes 80% assembled) didnīt use any thread lock at all. The gear got loose and therfore the gap between gear and motor plate widened considerably. This lead to binding between gear cover, (outer) idler gear and spur gear, which damaged both gears.

The gap between motor plate and gear should be minimal, almost non-existent. I thread-locked the screw and made sure the gear is in the correct position, and didnīt have any issues since.