Thanks so much for your feedback. I'm going to try tonight to see if that one screw is truly locked up.
Be really careful. I would say its only locking the mirror up if you're getting that puzzling opposite indicator that you should tighten the super tight screw and loosen the super loose screw based on the out of focus star pattern. Also, if you have more than 1 very loose screw I wouldn't point the tube straight up at Zenith because the risk of the secondary falling onto your primary and destroying the scope is much greater in that orientation.