70 Duster window's

The bearing assembly right behind the handle may be the problem. It should have a bit of backlash or lost motion in turning, that is by design. If it has a lot of loose motion or wiggle in the handle, it's worn.
The good news is that piece can be replaced. Get better parts from a later model rear doors. Just drill out and replace 3 rivets. New grease, etc.. that others have suggested.