I'm taking our 19H in for leak testing in the next couple of weeks. Not sure how common this procedure is, but a local RV repair shop uses positive pressure inside the trailer with a bubble solution on the outside to locate any air (or water) leaks in the shell (kind of like looking for propane leaks). I know I have a leak somewhere in the back corner of our unit but have been unable to find it visually. Hoping this gets results so I can fix the source before I start repairing the damage (soft spot on floor). Similar to you, I bought it with the leak, but in my case the dealer claimed the leak plugged; I'm not so sure as I think the area grew this summer.
2011 Jayco X19H (purchased 2015)
2008 Jayco 1007 PUP (purchased new, traded for the X19)
2012 Chev Traverse LT with TP