I had the same problem with mine, so I just took the door panel off, removed the control box from the door, and took all the screws out of it. Then I undid all the tabs of the box and opened it up, you can only open it up slightly, I'm not sure why but when I put it all back together everything was 100% again.
I'm assuming that the lockout switch either wears out, or is just prone to gettting dirty. The buttons are the same style as the ones you'd see inside a remote control for your tv if I remember correctly. So they're no the most reliable.