I just read this and see that nobody has replied to you. Sorry to hear about your troubles.
I did some research on the forum this morning and located a couple of threads where Windjammer (and other Forest River V-nose trailers) were having some problems with cracks similar to yours, although they were mostly above slides and were all on trailers from model years 2011 and before.
I am not sure if he is still the guy to contact, but each of those threads pointed those with troubles to contact Doug Fought at Forest River. Here is the contact information contained for him in those threads:
Doug Fought, Warranty Manager
Flagstaff / Rockwood Divs. of Forest River