Hey ABBrittain,
I want to help you so I created this thread here.

What computer do you use, especially what GPUs and what driver on each pc?

Sonds more of DXVA issues to me, not related to MPC Video Renderer, anyway, we will see

Be sure to use MPC-BE 1.5.4 available also here, not MPC-HC, because full support is only on MPC-BE