Power Window question, help? Anybody? Options

[95CelicaST]

The other day I went to roll down my passenger side window and it made a nice clunk, followed by many more clunks on its way back up. When I roll it down, its as though something is lop-sided inside. it will roll down a bit, studder, roll down some more, studder, and clunks here and there at any random point in time. When I took the door panel off I could not see anything out of the ordinary, so I assume it is my regulator, but that doesn't really explain the clunks..

-this is an aftermarket power window system. My car came with Manual windows.
-no I don't know where the work was done, but I'm sure I can find it in the receipts I have.
-regulators have been replaced once before. I remember reading that in one of the receipts. I believe it cost somewhere around 235 bucks.

any help?