HI Dave yes the expandable drums wear out sounds. Sounds like
yours need to be replaced. I have never heard of a way to
refurbish them wich would be nice since they seem kinda pricey.
When you do get new ones make sure never to put a stone to it
with out the belt in place or you will be replacing them again.
(learned the hard way.) If you have any more lapidary questions
feel free to e-mail me off line.