On each window there is a "track" at the bottom where one end of the regulator arm with "toggle" fits in so it scissors up/down when the motor is activated so make sure the track has plenty of grease so it slides easily.
Other issues can be from the window felts/tracks that keep the window from ratteling get old/brittle and loose affecting the windows movement, dargging/binding etc.
I would also make sure the other end of the regulator arm with teeth is mating up properly with the PW motor gear AND that it "pivots" off that round "stud" in the middle going into a hole in the sheetmetal for balance. If there's any issues with the motor the regulator arm will want to "pull away" out from that balancing hole affecting the window movement.
PW motors will fail eventually but I would "rebuild" the OEM original rather then replace it with an after market that more then likely won't fit as good as the original. If you can't rebuild it yourself take it to an Auto-Electric shop and let them do it where it's no more expensive the buying an after market motor, naturally the rebuild kits are less expensive.
The alternator is also going to play a part in this so make sure it's putting out the right amount of voltage to the motor.....
Good Luck ~ :thumbup