I have a 1/2 HP Craftsman garage door opener, model # 139.53635SRT. The door closes all the way and then retreats to the wide open position and stops and seizes against the stop bolt. When I hit the wall button to make it move again, it just makes 2 humming noises. I release the tension on the bolt, try it again, and it does the same thing. I can close the door, manually, without bucking and it closes smoothly. My father-in-law thinks it may be a bad relay that controls the stopping of the door/motor. I donÂt have a manual. Any ideas?