I've got 2 fatbikes - one is my daily driver with more than 2000 km on it, most of that on cheap Kenda k1118s at 30 psi. rolls fast (fatbike fast anyway) and behaves exactly as I expect it to.
I've never experienced the phenomenon you are experiencing. Not even in the winter on Jumbo Jims where I generally ride at 6-9 psi.
Good luck