Thanks folks. I'm actually a fairly experienced rider with 700 miles on my board and I do wear skate shoes (Vans) when riding, so I would think that's not the issue.
I actually forgot to mention on my original post that the issue is only on heel turns, when I deweight my toes. I can't imagine doing a sharp heel turn without deweighting them like I do right now though.
My stance is pretty much what you see on the Onewheel marketing material for the front foot but I have smaller feet than that (I wear 9 - so maybe that's it?):
I liked the tip about the felt circles, I will try something like that too.