In case anyone else is experiencing this...

I ran into a problem where the AJA driver (for their T-Tap monitoring box) was causing slow startup issues, sometimes to the point of hanging indefinitely (or beyond my patience). I also could not install other AVX2 plugins (like Boris BCC)- the AJA driver installs two files there which don't seem to play well with others.

I ditched the hardware for the Blackmagic UltraStudio 3G ($115) with their driver and everything is running fine now.

Thanks for the info.