My garage door opener does not work. The remote and hardwired button will engage the motor but nothing in the chain or screw mechanism moves. It appears the part that slides along the track has disengaged from the counter part that moves it with the motor but the disengaged part does not move as well. Upon pressing the button you can hear the motor make a complete cycle (the door opening and upon completion the motor continuing into the closing cycle.) Is there a way to repair this?