[JRTJH]

Trust me when I say that your trailer is subjected to much more "stress in its joints" by driving over a railroad crossing at 60 MPH than you'll get from jacking one end of a trailer a couple of inches....

The molding (door header) is screwed onto a beam that runs across the trailer and is attached to the ceiling/roof joists. If you look, you'll probably see 4 or 5 screws holding that molding in place. Remove those screws and you'll find the door track under it. The separation is "purely cosmetic" where the wood cover meets the door frame. Remove the wood cover and inspect the steel door rail under it (the part the door rollers move on). I'd suspect there's no damage, maybe a loose roller rail or a loose wood cover.