Sorry you are finding issues on your "new to you" trailer.
Jayco, like evey RV mnaufacturer, has their issues but ultimately I think they build a decent unit for the price. You are't the orignal owner, is it possible that the prior owner had some extensive side wall work done and didn't tell you? Maybe what you are seeing isn't something that was done by the factory?
I have had 2 Jayco JayFlights and I have not had any serious issues.
2007 Chevy Duramax LMM/Allison
2012 Jay Flight 29QBH
2012 Jay Flight 26BH (Sold)