Window 2 cents worth
I found that servicing the motor didn't yield much (unless there is an obvious electrical fault) - it was getting the track spotless clean and well (read lots) greased. I used Kleen Flo "extra heavy duty, multipurpose lithium based grease" - any white lithium grease is probably fine . The first window I did got the least grease and is the slowest.
Grease the track and put a gob on the nylon sliders that run in the track and slide it from one end to the other several times adding grease as needed. Open the gear box and "differential " gear that drives the regulator wheel clean and pack with grease. Clean all the teeth on the gear toothed regulator wheel and grease. Clean all the pivot points and lube with a spray lithium latch grease. The only thing I did with my sardine cans was a drop of oil on the drive shaft.
Tidy up any goops of grease and reassemble.