Interesting, I would do the opposite of what they suggested. The door on these is overly sensitive to out-of-level situations. I would always ensure that the trailer was properly leveled before installing the door. If the stabilizer jacks are too tight, it can cause the door opening to squeeze together at the top a bit through the flex. If you look closely, you might notice that the door opening is a bit wider at the top than at the bottom to allow for this.
I would check my level carefully to see if that might contribute. Do you use the little spirit or gravity ball levels on the trailer box? It is possible for these to get a bit off-kilter if the glue is failing. Use a large spirit level to confirm that the trailer is level as a cross check. I have a big 6-footer that I use occasionally to cross check my little bullet levels. If your trailer is out of level left to right, there can be enough flex in the roof supports to cause what you describe.
2011 Jayco X19H (purchased 2015)
2008 Jayco 1007 PUP (purchased new, traded for the X19)
2018 Nissan Titan Midnight Ed.