The previous owners apparently had a tire blowout so bad it ripped a metal frame support right off the frame. It also did damage to the wheel well as it had been rebuilt with plywood at some point. I didn't notice the missing frame support when I bought the trailer. The wall spanned from the rear of the trailer over the wheels to the door. It's no wonder the pressure from the wall caused wood to squeeze around the rear frame support.
Holes left when the support was torn from the frame. Let's fill those in a bit and fix that crack.
I couldn't find anything pre-built so I used what I had, some angle iron.
The rusty frame made it difficult to get a clean weld. If I'd had more experience I probably would have cleaned it up with the angle grinder first.
All done. No saggy walls now. You can see in this pic how at some point a 3" lift was added to the spring shackles. I don't like how long and unsupported those shackle supports are and I might try to fix it at some point.
No pre-built wheel well solution that would fit my needs so custom galvanized steel and staples did the trick.
After this was built I used caulking and rubberized spray to waterproof it.
You can see why the kitchen had to be removed in order to properly rebuild the floor and wheel wells.