I just read your post, my first thought is exactly what you found, gear train failure.

I think the epc code was from excessive metal build up on the contacts.

There is a flat needle bearing that is inside the planetary, the bearing fails and the little bearing rollers fall out and end up in the planet and ring gear teeth causing a complete gear train failure.

We just had this in the shop about two weeks ago, we had to jack a rear wheel up off the ground and use a pusher just to get it in the shop.