UI freezes when selecting 85/100/120/144hz

Hey Everyone,

I recently put together a hackintosh with the following components:
* Gigagyte Z370 Gaming 7
* Intel I7 8700
* GTX 970
* ASUS ROG PG279Q monitor

I followed this guide, and because building a hackintosh is still very new to me, I didn't change anything really. So all of the pre-post configuration and kexts are the same:
http://hackintosher.com/guides/high-sierra-install-full-guide/

I also used this guide to get the GTX working:
http://hackintosher.com/guides/properly-install-nvidia-drivers-high-sierra-10-13/

The issue I'm having is this - setting the refresh rate to 144hz (with SetResX or natively in system preferences) causes my UI to freeze. I tried 85hz, 100hz, and 120hz as well with the same results. This happens when I'm connected using the DisplayPort cable, and I'm currently working around this by unplugging that cable and using HDMI (at 60hz).

Is there anything special I should need to do to be able to use the higher refresh rates on this display?

Thanks for the help!