I have a 2016 Flagstaff 22FBRS. I had the same type of odd gap where my floor to ceiling cabinet (that has the TV set, stereo, and small bottom cabinet) was supposed to attach to the exterior wall. It was pulled out over time by pulling on the TV set to swivel it around.
In my case, the side of the cabinet was only "attached" by a thin bead of tan colored caulking. Luckily there is a 1x2 right behind it, so shoving it back into place, putting in 3 or 4 wood screws, then a strip of molding solved the problem......I hope. Try to see if yours has such a strip behind the gap and then get some wood screws. Good Luck to you.
While Rockwood and Flagstaff have some very nice designs, their carpentry and interior construction is terrible. I'm an OK carpenter so I can fix this kind of crap and have made many repairs
Flagstaff 21 FBRS 2016 Jeep Grand Cherokee V6 Equal-I-Zer