Craftsman Garage door opener.
First off thanks to who ever can help me. I have a 3/4 horse craftsman model number 139.53924. Got home today door opened 3/4 up, then slammed down shut. Went into garage hit button, motor just grinds turning the drive screw. The plate that the trolley attaches to locks in place, but when the door is fully closed or open the plate pops out of track. Did a pin break? Or What might it be. Motor and screw seem to be fine, trying to not replace whole unit, please advise. Thanks, Justin