...Spray the rails with silicone lubricant at the first sign of binding. Like any surface that rubs against another, the surfaces between the rails and glass need to be lubricated to provide friction/binding free operation. This maintenance issue is not limited to the VX, however the lack of service to this component by ISUZU techs may be. In most cases it is done when the vehicle is taken in for routine maintenance along with lubricating the door and hood hinges, cables and such. Just as you would not ignore engine oil, or consider it a nusance to change it on or before schedule, the little details of lubrication mean a lot to long term trouble free enjoyment of the vehicle. Hope this helps