That sounds like the tracks needed "finessed" and the tabs probably need re-glued. That was the original problem that I had fixed by the dealership (and their body shop).

My latest problem (and the reason that I started this post) was was I thought to be the regulator, but actually turned out to be the motor. More specifically, the gear that meshes with the regulator was worn out, therefore replacement of the entire motor assembly fixed the problem.