Sounds like your track is off. Gonna have to take the door panel off and see what is going on behind it. My experience with these cars (My 1969 tbird personally) is that the rivets holding the track onto the window frame break off and then the window sags causing it to go up unevenly. This can also lead to the scissor lift bars to bend because of the uneven weight of the glass. BEWARE if you do intend to work on the glass it is VERY HEAVY and I don't think it is tempered glass. So if it breaks you could get some very nasty knife like shards. Just be careful in there. as with anything of this age really.