I have a sears craftsman older door opener model 139.53615SR I changed the gears and put it together and it worked great. About 3 weeks later the chain link connector broke and I had to repair that. Put it all together and now the door opens about 14" and closes about 14" I never touched any of the up/down screws and it seems they are still in the right place. Its like the door automatically goes back up after about 14" like something is stopping it. Any suggestions? Thanks...