I am on the other side of an opinion. Life is to short to stress over a plug that's 2 for 5$ on amazon. Any rust on a hinge is likely to reoccur with replacement of the same crummy material on a new one. Is it worth the hassle of bringing it to a local dealer that you didn't buy it from, leave it there for who knows how long while they service customers who did buy from them, for this problem alone ?
Oh it may have never been titled, but its not brand new, its almost a year old.
But absolutely if its worrisome for you, call Jayco. I wouldn't.