I have a Craftsman 1/2 HP GDO, model 139.536445SRT, manufactured 10/96. Whenever I activate the opener, the worm screw moves about 1" to and away from the garage door, which in turn, knocks off the interrupter cup. This causes the opener to reverse directions and stop. I called a technical support number and they said there should only be about 1/16" of play for that worm screw to move. Mine moves at least 1". Any ideas on how to eliminate the play in the worm screw and eliminate the interrupter cup getting knocked off?

Thanks in advance.