You need to understand where the frame has failed in order to define a fix. That means at least dropping the skin under the gooseneck to see everything. I had a unit that when the brand switched to the notched front cap, then the front crossmember also had to be notched rather that straight across. Only problem is that Lippert made the frame notch greater than was really needed. The front crossmember attached to the main frame just a few inches ahead of the rear crossmember. The result, too much flex. I didn't have a failure, but Lippert agreed the design was poor, they added a forward extension on the main frame rails and relocated the front crossmember further forward. Also extra stiffner for the rear crossmember. Result, less flex. Lippert changed the frame design on new units within a few weeks. My repaired unit was fine 6 yrs later when I traded it in.
People don't realize that the trailer body, meaning walls, etc. help stiffen the frame, and if the attachment points between the frame and body fail or become loose, then again, the frame flexes too much w/o that extra support and something in the frame will then fail. Patching cracks in the skin does nothing for the underlying problem and cracks will return.
