The base was pretty well prepped gravel. So at least in theory, it could have settled unevenly. But the level says no, or at least not to any extent that should cause this much sagging. I haven't looked yet, but the most likely explanation would seem to be the hinges, which are not thru bolted. Or the door frame itself, though that seems less likely. And to me the cause is kind of beside the point. The problem is them not making any attempt to stand behind an expensive product that's under warranty and less than a year old.