the guide that goes in the vent window side may be bad.. You will have to pull vent and window to replace them and then adjust slide front a nd back. I replaced every thing in my 69 doors window related and took a bit of adjustment and some graphite to finely get them to go up and down easier , Still a little tight but I think will get better the more I used them When you pull vent window have some help to put back in the door glass and the vent have to go in as one piece . there is a guide alsothe could be bad in the back slide for the window. The only other thing may be bad window crank up , Can think what it is called could be bad , You could try some Lubricant on the that ,WD40 or some thing
Just notice you a Former Marine !!! Semper Fi