Probably you have a bad reed switch giving you this fault. There is 4 in total 1 for open slowdown and 1 for open final. Then 1 for close slowdown and 1 for close final. The close final I would bet is the one to change out. There’s a magnet on the door roller assembly that makes the reed switches change state. Make sure that there is about 1/8th clearance between magnet and reed switches.