Car is 92 300E.

Driver's side window will always go down but lately it does not want to go back up. Had this problem for a year or so but it's getting worse. Tested switch and it's fine.

Since the window will go down reliably but not up reliably does that mean the problem is with the regulator and not the motor?

Can the regulator be reconditioned to function normally or will I have to replace it?

Never hear any machine gun noise like something slipping on gears.