Not the most exciting subject, but I have a 94 pickup with a driver side window that always rattles most when open just a few inches. It gets quite noisy on steadily uneven roads. Yet, this happens to be one of the most practical positions, where hot air is allowed out without a blast of air from outside. The passenger window is often in the same position, but it does not exhibit the same issue. I have had the inside over off while working on something in the door and have checked out the parts related to the window track but came up short on spotting a problem. It seems likely it is a single part that has become worn but everything looks okay including the felt-like bolster and squeegee flap on either side of the glass at the top of the door. The bolts at the bottom of the glass are also snug, but something is still loose and the window has acquired some light vertical scratches likely related to this problem. I actually filmed a clip of how the window clicks when wiggling it from the top in the most problematic position.