> >I have a nice desk chair,
And cheap plastic casters? Get some new casters.
There is something jammed in the axle area.... thread, hair, carpet
fibers, something. I don't think you can successfully they them apart
and put them back together. The best bet, if you keep them, is to use
needle nose pliers to remove whatever is jamming them/wrapped around
the axle, if you can access the debris.