Power Windows not working right - 99 Buick Regal

We have twice replaced the regulator in the drivers door and are still having issues with the power windows. The drivers window is still working and the rear window on the driver side works, but very slowly. Neither window on the passenger side will work. What else could it be? (We’re getting ready to sell the car and I’d like all the windows to work when we do)

Thanks in advance

Are you doing the replacing yourself or is someone else? Either way, what kinds of things have been done to check the whole system rather than just assuming that it needs new parts? E.g. has the voltage at the switches been checked? The switches themselves been cleaned and checked? Tired or bad motors/regulators are one problem that can occur - the other problems are in wiring & switches.

If you are using aftermarket parts, that might be the problem. I’ve had several substandard regulator/motor parts for my 1998 Regal. The last replacement went in easily and the motor didn’t bind at all. It could be the parts you use.