[VaSteve]

Originally Posted by Por_sha911

I had the same symptoms. It drove me crazy (short trip) for an hour or more. Turned out to be a spider web had a leaf stuck on it and the sensors that protect you from the door crushing something or someone would reverse the door when the leaf got about two feet off the ground. The system I have has a little light on the sensors and when the beam is broken the light goes out. See if there is something that breaking the beam before you start adjusting the closing force.

^^^ This.

I also have all kinds of wood scraps, bicycle pumps and the stuff of life jammed in the edges of the garage near the tracks. Sometimes something shifts a little and the door will catch it go back up. It doesn't need a lot of force to send it back up.