Does it do the same thing with the top up and down? With the top down, these cars have more flexibility that when up. That being said, I would check the sills and door posts for possible corrosion. When a car starts to have the doors dropping it can be a sign that it is starting to lose the structural rigidity because of the dreaded tin-worm.Has anyone had experience on early models off doors dropping and not closing properly without a hefty bang. Can they be adjusted easily ?
Then you may need to check the alignment of the glass in the door.The doors do seem to close easier with the top down. I also notice that sometimes on the passenger door even when it closes properly the glass does not sit into the rubber and have to pop it in by hand.