Begining to delaminate

That is a rather unusual place for delamination, but I suspect you are getting water in through the seam behind the vertical corner molding. The screws are not sealed and that is usually where it starts. The material behind there is probably heavily rotted. Internal structure at the corners is frequently rotted by the time a coach is 10 years old. Just today, I did a repair on an '08 in this exact same area because the corners were all rotted and there was nothing to screw the molding into. When we pulled the molding screws out, the heads fell right off the rotted screws. I would suspect your repair will be more complicated than just running some glue down into the delaminated area. It is probably rotted and likely wet. There are a number of ways to approach a repair like this, but neither are particularly appealing. I'd start by removing the vertical molding and see what the structure looks like in the gap. If it is rotted and wet, you are going to need more than glue. You may have to cut the filon in this area, replace the underlying material and then refinish the exterior. Bottom line is that you need to do something. The delaminated area will expand if the situation is left unattended.