From looking at the pictures, Jayco is attempting to add braces to the very thin alum. side wall. The issue is the main frame is flexing and causing the crack. They can try to stiffen this wall up but you will still have frame flex as they are not correcting the root cause of the problem. This is why it will crack again. My Open Range did the same thing. They add a expansion joint and it never reappeared. They then added the expansion joint to all production units the following year. With the heavy weight of the units, you will always get some frame flex, this id why you see an expansion joint on most FW.
The expansion joint doesn't fix the problem, it's just hides the results of it. The frame over hang flexes too much for the trailer walls to handle. Although if they put enough steel in there to make it stiff then everyone will need a bigger truck.
You’re correct on the expansion joint. Much easier adding the joint than having the factory keep trying to repair the crack numerous times. Reality is you will always have some flex in the frame is this area.
2019 Eagle FW 321RSTS
2015 GMC 2500 HD 6.0 Gas