I just noticed the same thing on the slide ends while cleaning our 2017 Wildwood this past weekend. I investigated around the edges and didn't see any source of water intrusion, but I was a little concerned. I'm glad to hear that you got word from the dealer, but I'll keep an eye on it still. My next move is going to be purchasing an awning for over the slide.
I did see this same sort of waviness on the slide of an earlier Wildwood when at a State Park over Memorial Day, which made me start digging into the awning idea. I never had a chance to chat with the owner of that one to see what year it was. I think I have a picture of theirs, so I'll dig that up for future reference, and post one of my own later.