I recently purchased Aladdin's Castle (Bally, 1976) and have an issue with the flippers. While the left flipper stays tight, the right two flippers (tandem) keep working loose, especially the bottom flipper. I've replaced the flipper shafts - the originals were very chewed up by the knurled cup on the set screw. But that only worked temporarily.
I saw in some previous posts the theory that it is the crank that is at fault. That the metal in the crank is softer than that in the screws and by continually re-tightening the set screws, it causes the threads inside the crank to strip. Is that true? Has anyone else had a similar issue?
FYI - I've tried locktite on the screws and they still worked their way loose after 10-12 games. Does that add even more evidence to it being a crank issue?