We have a 3 car garage, with 2 doors, 1 of which is a 1-car width door. This door has stopped closing automatically. It can be opened, but won't even nudge it 6 inches, when I try to close it. If I release the door from the traveling thinga-ma-bob that pushes and pulls the door, I can than manually close the door. When I then activate the closing cycle, the traveling thinga-ma-bob works fine and goes all the way to the door and reengages. I can then use it to open the door. The first thing I did was to check the sensors, that they weren't blocked or that the lenses hadn't gotten dirty. If that were the case, I don't think the motor would move the traveler, even when not engaged. Maybe I need to lubricate something? Any advice?