Auto body repair & detailing: Ford F-150 door glass goes down rough, ford f 150, regulator assembly

Question
Meaning it reaches mid point when going down, stutters and stops. Can't explain it but after removeng the inside trim to get to the mechanism and glass. it appears there may be a slight bind, I tried lubricating the slides, did not seem to affect it. After a few hours of frustration, I added silicon lub to the side verticle glass slide rails, yes they are felt covered. This seems to improve things quite a lot. Any ideas or suggestions?

Answer
replace the window regulator assembly. The roller on top of the regulator has gone bad, not allowing proper operation of the window. Replacement is the only option, look into aftermarket regulators. New OEM are unreasonably priced, an aftermarket will cost about half to a third as much. Bill