The windows need periodic lubrication, and sometimes an adjustment. WD40 is an excellent lubricant, but use it just before washing the vehicle. Spray it carefully along the two sides of the glass, in the seam, on the felt.
There is one adjustment on each side window. Along the lock edge of each door there is a short window guide which controls that edge of the window. It has one bolt at the bottom of that guide, and the top edge slides up into the window glass opening near the door lock button.
That adjustment basically keeps the window glass flush into that guide, if it becomes tight it would bind, if loose the glass would shudder going down. To make that adjustment is simple, remove the door panel, with the window down. loosen that adjustment bolt(13mm I believe) that is several inches from the bottom and lright next to the door panel edge. The bolt holds tension on the guide by a bracket attached, simply push the bolt sideways, towards the hinge, with mild pressure. It can go either way a short distance, that is the slack being created in the guide/glass. Take out that slack, and tighten the bolt. Test the window, adjust more if needed.
Try WD40 first, then maybe it might need adjusting. See the lowest gold colored bolt along the right edge of my RF door. Good luck,
