Diagnosis
The down force limit is set too sensitively, or the torsion spring system is binding.
How to Fix It
Adjust the down force. On the logic board, turn the DOWN limit potentiometer (labeled "DN") clockwise by 1/8 of a turn. Test the close cycle. Repeat in small increments until the door closes fully without reversing. Do not exceed 3/4 of a full turn.
If That Didn't Work
The door itself is out of balance or the tracks are binding. Disconnect the door from the opener by pulling the red emergency release cord. The door should stay put when lifted halfway open. If it falls or is hard to lift, the springs need adjustment by a professional.
Heads Up
After increasing the down force, test the safety reverse function with a 2x4 on the floor. The door must reverse on contact.