The front channel is the only one that’s adjustable. Need to have the upholstery panel off to get at the slotted bolts at the bottom of the channel. At the top of the front channel is a small screw that holds the top in place. It allows for a small amount of fore/aft adjustment. The rear channel has no adjustment. But it could be that it’s not properly seated or fitted down into the retaining slots in the door frame. If it’s not properly seated, it would definitely be pushed out toward the front of the car, creating a chance that the glass would be in a bind. Good luck.