I bought a used desk type chair at a garage sale this weekend.
It was a "better" chair, but the casters would not roll - at all!
It is five or six years old - the local warranty manager for this line managed to figure out a way so that they could replace the casters/rollers and the hydraulic thing that raises and lowers the chair - AT NO COST TO ME!
If you want to know who and what, send a PM to me and I will be delighted to tell you.