garage door opener 'down limit' keeps slipping
I have a problem garage door opener, I keep having to adjust the bottom limit of the door travel by turning the set screw back (up) a few turns. Then after a week or so it has apparently slipped, and the opener starts acting like it is trying to shove the door into the floor, which has severely stressed the door where the arm is attached. I keep adjusting the down limit to compensate but I have not yet tried to fix the damage to the door where the arm attaches, until I solve the problem causing that damage.
Has anybody else had this problem? The door opener is a craftsman 1/2 hp model.