I have a 13953664SRT2 Craftsman 1/2 HP belt drive garage opener. My power was out temporarily and I manually released the door. Power restored, I tried to reconnect the trolley but the trolley kept 'missing'. After several attempts, the trolley moved all the way to the door end of the rail. Now, when I attempt to open the door (with or without the door connected to the trolley), the motor just hums but does not move the belt. Hitting the opener again, the motor changes directions but just hums. Any ideas?