John, that’s a shame, sounds like you did everything right. Only thing I can think of is maybe the humidity was too high and you had trapped moisture that took time to work it’s way our. I use Tamiya primer most of the time without issue.
I won’t use Rusty-O on anything except maybe and old wheel barrel. Had too many problems with cans that don’t spray and when they do spray go on too heavy. I’ve heard people have good luck with Krylon which I used years ago but can’t can’t around where I live.