Probably somebody that's worked on this model knows exactly the answer to your qustion, but I'm having a hard time visualizing it. It seems that there is a tuning vernier that isn't driving what it's suppose to?
Can you possibly post a photo or a sketch showing the specific internals that are giving you the problem? (You can't post a photo directly on this website, so maybe use a free photo hosting service, like: http://www.imageshack.us/ )