Crew cab rear door/B pillar sagging.

[TWC]

1964 Crewcab, the passenger side door drops about a half inch when opening it. It doesn't drag but as soon as it leaves the door fame it drops. I think I can see the B pillar flex when I do this. Has anyone seen this? At first I thought maybe the hings was bad but now I'm assuming there are some panels that make up the pillar that have fatigued welds. I don't see any rust in the pillar inside or out but can push on the seam that makes the top inside of the B pillar from inside the truck with both doors open and make it wiggle very slightly if I push very hard.

[HemiJoel]

I would inspect the body mounts and make sure they are all good. If anything in a body mount is compressed or sagging, it will cause the cab to twist, throwing off the door alignment.