Recently picked up three 4506 and one 4566. All of them had some form or another of the clicking going on. The 4566 was the worst. Simply bent forward the copper tabs on the 4506's, and the solid copper tab at the top on the 4566. Good as new.
No more clicking and much smoother too. Ain't the internet great! Solved this problem via google and here I am. Thanks to all.