There have been some issues (tho not widespread) with regard to rust, and in some cases leaking along with it, at the seams, especially some of the spot welds, but also up around the gutters. It's a good idea to get a ladder and get up there and check out every now and then. I've found no evidence of rust or separations, but, speculation is that a few vans that were painted on a few Friday afternoons may have gotten a coat or two less than they should have. Depending upon what the root cause is (bad welds, rust) it should be repaired under warranty, as the paint and rust warranty is a little different than the standard and drivetrain warranties. If it's stress related, then the warranty may not cover it (not that I'd offer up to the dealer any possible causes other than a manufacturer defect, of course).
What I would do is, take the van to a Mercedes dealer and have them take a look at it. Just tell them you'd rather get a qualified opinion before taking it to a Dodge dealer.
Then, take that information to the Dodge dealer. You may end up repairing it yourself, which may be the best thing in the long run, anyway.
Slow and steady, even in expediting, wins the race - Aesop