Hey Guys thanks for all the advice so far,
Mike- My father is a logger and has had logs sitting for several years that I busted up this spring and are showing 18-20% moisture content now, and also had 30 cord split up that's reading a few % lower, and the rest I've got from buying and reselling in better markets, again making sure it's good on moisture.
I would agree going the mixed hardwood route may be one way to avoid this, but the oak brings a premium and I'm one of the few supplying 100% Oak (maybe that's a sign to switch) And it's a lot more difficult to get mixed hardwood firewood than it is to get oak firewood in my neck of the woods.
I wish there was a better way to show to unhappy customers that it's not the wood than just saying I've had very minimal complaints and the wood is showing good moisture content. But like mentioned some people just never are happy.