[68JOHNDEERE]

The vent wondow getting hung up in the seal would be caused by the upper pivot point on the outside of the vent assembly.

I would first check that the mounting screws in the door jam are tight. This pulls that pivot into the door, thus the glass moves forward.

Second, open the glass and see if there is excessive play in the pivot rivet. If so that needs to be replaced.

Third you may have to adjust the pivot point with a pliers. You would want to move the pivot forwards toward the front of the truck a little to pull the glass out from dragging on the seal.

Hope this helps.