And the problem, of course, is that the latch tries mightily to hold that 1/2" gap to 1/4", meaning that it tries to lift the lower door and pull the upper door downward, both of which require flexing the wall. And the walls don't want to flex. The bottom line problem is most likely that the wall of the shell and the wall of the lower body box are not quite parallel to each other. This is easy to adjust, so I will simply point you at three threads where we have discussed the problem and the fix.
Let us know if this isn't the right answer.
http://www.trailmanorowners.com/foru...read.php?t=924
http://www.trailmanorowners.com/foru...ad.php?t=17249
http://www.trailmanorowners.com/foru...ad.php?t=16360
Just FYI. Before TM starting using the mtal latch with the hook - this is what you have - they used a simple rectangular block of nylon, maybe an inch square by 1/4 inch thick. One corner of the block was screwed to the edge of the upper door, which allowed the block to swing down and overlap the edge of the lower door. This kept the doors together in the swing direction. But since the block had no actual hook, it didn't try to keep the doors together in the up-and-down direction. The lower door could simply slide up-and-down against the block. To decouple the door halves, you simply rotated the nylon block upward. Simple.
Bill