Just replying now because I only just received my replacement motherboard late last week and spent the weekend setting it up. I posted a reply that may help on your original thread here
try using the compile script mdPlusPlus created and posted to github.
It will patch and compile the latest kernel for you. Compiling the kernel seems to be the best option if using nvidia on the host (I installed the nvidia drivers before doing the kernel patch). It seems like there is a bug in the pre-compiled kernels or that they are hardware specific. So maybe they were created with AMD gpus intended for host and another AMD/nvidia for the guest.
It fixed the issue for me
May have to go through all this acs patching thing again once I put my new workstation together and replace this DDR2 RAM system from 2006.