Same thing happened to mine. I found out that the aluminum bracket that holds the worm gear was bent from someone holding the close switch too long when the door meets the stop. We took the mounting screws out and replaced them with small bolts, made a heavier aluminum bracket, lubricated the worm gear & track and then swapped the bottom rollers out for the top rollers. Evidently they went unseviced for a while and wore flat spots on them which caused the door to grind and jump every once in a while when the roller actually decided to roll. It didn't speed the door up, but it was smooth as glass and a lot more quiet.

Sorry for sounding negative. I've repaired a number of the mechanical and hydraulic Cigarette doors in the past. The engineering left a bad taste in my mouth for the added bling factor. We always had to add the thru bolts and modified brackets to get things to be more reliable. The rollers even on the original design are ok if serviced but eventually need replaced as they flat spot from the pounding. Good luck with your project.

How do you get to the rollers to replace them?

I would like to know as well, I have an 04 Top Gun. Pics would be nice,

Behind the passenger dash panel