Sometimes when the controller is not getting a good enough connection it will not read high amperage soon enough to shut down the motor in time putting additional stress on the three sacrificial blocks between the hub and ring of the main plastic gear so that they disintegrate instead of destroying the gear. I just use some 3/8 inch ID lawn sprinkler plastic tubing with a piece of 3/8 inch rubber rod/dowel inserted in the middle to replace them and everything then works as it should. They are just round rubber/plastic rollers or perhaps dowels for lack of a better word and are just there to absorb shock and help prevent the plastic gear from stripping. They are about 9/16 inch in diameter and around 7/16 inch thick.
Someone posted a while back the model number of the power window motor you can buy at most automotive parts stores to replace the step motor for less than most RV suppliers sell the repackaged motor for.
Its very similar to this though I'm not certain if this $15 Dorman replacement gear for Fords is the one that matches 100%:
The gear with the three shock absorbers can be had without the hub for around $10: