Patrick, I feel you;) My problems are with an other site, it's publicly noted, and I haven't had such problems with Stockxpert, but I know how it feels to have images rejected when they ALL go through inspection on Shutterstock (and it is obvious we all choose SS as the norm, full stop, the quality there is superhigh).
I suggest you write to user "skapsinow" (I believe his name is Steve) on Stockxpert and ask for a revision. He's been of great help in the forums and I can see he's always amicable. If you're 100% sure on your arguments than go for it. I'm think he might be able to help you (unlike Scout's tickets, for example)
)
And good luck!