[1retired06]

Yes, I would worry about it. It is something to worry about if it is deep, as moisture can cause delamination. And it may spread. And Keystone may pull the warranty period argument on you. If serious, an expansion joint is the normal fix, or repair of a broken frame weld which requires peeling back of the fiberglass and welding and follow-up body work. Labor intensive and expensive. If the crack is superficial and not into the fiberglass wall itself, not so much to worry about, and sealing with caulk may be enough. A 3 foot long crack would be serious to me. I would fight Keystone, worst they can do is refuse to fix.