Make sure all the parts and bearings are good and clean. Dirt that gets ground down into the "hole" can be a real PITA sometimes. Especially when people don't clean it out every once in a while. People will sometimes give a platter a real good cleaning, within an inch of it's life, and forget to get down in that hole. After a while the brain starts to stick and the payour arm won't follow the motion of the film correctly. Getting all the junk out of there can seem to make all the difference in the world sometimes.

Anyhoo... Once you get the thing put back together, just he way you like it, hold it up the way it would be if it was installed in the unit and test it out. The filter card should be able to swing freely under its own weight without "snapping back" or getting hung up. It needs to make a smooth, gentle travel in both directions. It may take a few tries to get it right but once you know the "secret" you sould have no problems.
 

Keep as little tension on those springs as necessary, and also make sure that they do not become tangled upon themselves, which can easily happen.

Keep those bearings clean and lubed!