I haven't ever rebuilt them, but I do remember one time when one or both of them kind of "came apart" a bit when I had it/them off. I remember fiddling with it/them, trying to get them back on so that they would turn freely. BUT, apparently I didn't get them on right.

I do remember regreasing one or both of them, and it's very possible I over did it. However, they do turn, so my guess is the problem is in the mechanism itself. I'll have to research how they go together.