I have a Mamiya Pro TL with 5 backs and I have this continuing problem with not getting more than 3 shots before the shutter release stops working. I've changed motor drives and I've changed the batteries in the motor drives and still I can't any more than 3 shots. I generally have to turn the camera off wait a few minutes before I can get anymore shots. Any ideas other than the possibility that all of my backs are defective or is this just an inherent quirk with this system?