Looks like something at one time was in the way when the slide was pulled in and broke a weld in the wall on the aluminum tube and has since had stress put on it and it bowed. Just my opinion based on photos.
Hope your floor is not involved. Going RV just had an episode, they removed the slide and replaced the floor for 3K - beats buying a new RV. We had the whole back wall replaced because of delamination, looked like the house that Jack built. Of course we started looking immediately for a new RV.
I have the same on my TT,which is 10 years old ,it looks like a seam under the Filon/ Fiberglass but it's not due to water, the Fiberglass Filon is very thin anything under it that is not perfectly smooth would leave a crease or buludge. I do have some delamination on my TT also, two very different things. I'm only speaking from my experience.
This is delamination, I did a major roof repair that caused this delamination, I'm not ready to tackle this yet, but when you press on the Filon/ Fiberglass it moves about 1/8 inch in, and is more visible in the heat of the day when it expands, I hope these pictures help.
Thanks for all of the insight everyone. We took it back to the dealer and they said it wasn't delam. I ended up finding a hidden water spot on the inside about 15 inches above the bubbled exterior. The dealer didn't seem so happy and I think they thought was being petty but I needed to know what was behind that wall. They agreed to take it apart and see. It wasn't wet underneath but was at one time. I asked them to spray for mold and mildew while opened. They refused to correlate the inside damage with the outside damage. I had my uncle look at it and he said it looks like the window above the damaged spots was popped out at one point. I have a hard time believing that the 2 spots are unrelated. So whatever was leaking was fixed by the previous owner. I hope it doesn't get worse! The dealer said as long as the leak is fixed it shouldn't. I'm not banking on what they say. Haven't been so pleased. Our 1st camping trip brought a few other things to light. But that's a whole other can of worms.