The wall needs to be held up by the frame. "If it were my trailer" I would remove the support with the bolt in it, install angle iron to go underneath and up the side of the wall an few inches, then weld new supports from the main frame to hold the angle up. Some holes through the angle and into the wall and fasten the two together. Remember to eliminate electrolysis always use a clear barrier tape in-between aluminum and steel. Now, I weld and fabricate however find a shop nearby and see what they can do.
I was in the heavy equipment industry as a career. We would repair semi trailers this way that had cracks in their main side rails, trailers that held 40k pounds and up.
Now being limited by the photos that is my best idea. More photos from further away would be helpful.