Seen this before.
As you know, the frame/body are flexing just slightly, too slightly separate the door latch/door jam.
Measure the gap between the jam and door, top and bottom corner, latch side. Both loaded on hitch and off.
From this measurement differential, figure if weight has to be removed or loaded behind axle or in front of axle to counter act frame flex door jam separation.
Two thoughts on this,
1) Slightly flexible frame(to a small degree) might ease TH road/offroad)damage/wear from a non compliant frame..?
2)Some have beefed the frame to solve this condition..?
