I stumbled across a post on the G**gle group where the poster mentioned having a rear body support brace weld crack. Since I'm anal, I crawled under my coach (02 41 select) and sure enough - same crack.
Based on the design, I would be willing to bet that this is a high occurence on our coaches, and I'd recommend looking under your coach to see if you have the same problem. You can look just in front of the rear wheels without having to get under the coach to see if you have the same problem.
I put a quick writeup with a couple of photos on our blog - RV Project: Rear body support brace crack | Roaming Together - Insights into Travel, Simple Living, and Digital Nomadism
Once I weld the additional supports in place, I'll post photos of that as well.