I had the same problem with one window. I could see rub marks in the lower side of the frame where the window was binding. It looks like the frame was compressed inward against the sides of the window when installed and was squeezing the window when it was closed. I loosened the screws on the frame then used all-thread and PVC pipe to make a jack-screw to spread the frame apart. I tightened the screws in the frame and the window now moves smoothly.
Check for rub marks in your frame. If you see signs of the finish being rubbed off lubrication probably won't fix it.
2016 Wildcat Maxx 23DKS
2011 Silverado 2500HD Diesel