I'm still re-reading you original posting
"The above the driver roof seam corner is coming apart on my 2015 Georgetown 377XL bad."
Thank god you were able to finally attach some photos of what your problem is. My original interpretation of your trouble was that you had a problem with an INTERIOR roof seam problem. On my rig, that means the plastic seam strip that covers where the larger sections of ceiling come together. The seams extend from one side of the rig to the other. I have several of them from front to rear. Just covers the gap.
When I look at your photos, your concern is clearly an EXTERIOR problem.....what I interpret as the black window framing. Your photos are little too close for me to know exactly where, but in the rest of the photos you can see the exterior of a slide and the grass around your rig.
Hope they get you fixed to your satisfaction, and keep us updated.
Ken and Terry
2010 Georgetown 330TS being pushed by our
2017 GMC Terrain toad (4 wheels down)