Those motors must put out some torque. I just repaired one of the rear windows on my "new" 240D. The PO told me that the PPO had the window propped up with a piece of wood. Anyway, what I found was that the motor was good but the regulator frame had been bent so the gears didn't line up. It appears that it had somehow jammed and tried to eat itself. Maybe the bolts holding the regulator to the door had come loose. All I had to do was straighten the frame, reinstall everything, and take out the piece of wood. I was actually able to fix something for $0.