Two years ago the controller unit blew a MOSFET about 5 miles from home. It was on a long hill, pulling hard and probably drawing a lot of current. Not as bad as being 20 miles out, but the route home is almost all uphill! No way to service in the field so I rode it home. I took it apart to repair, but decided to just replace the controller with a unit having a higher current rating. No issues since.