Our new-to-us 2016 Rockwood Premier's door goes in place great on the sides, but there is a large uneven gap across the top between the wall and the door. The gap widens from one side to the other. This is a significant gap. I stuff paper toweling in it and have a hard time keeping it there. The camper is definitely level. Both door and wall look fine in and of themselves--no obvious warping, but they just don't fit. There are no plastic pieces at the top to hold the door in place as there are on the sides. We were wondering if the top was supposed to have those pieces?? Any ideas as to why the gap exists or how it might be fixed would be appreciated.