Ok so after updating my 5,1 with RX480 to 10.13.6 I started getting bad graphical glitches on the bottom third of the screen with display port. It was working fine before the update and is still working fine with the HDMI. I guess I'm ok with sticking with the HDMI but will need to get a newer cable to be able to enable Freesync. Has anyone else run into this? Any ideas on where to start?