I have a desktop setup based on a Gigabyte AORUS GA-Z270X Gaming 7 1151 7th Gen motherboard. I've been using a HP Z27 monitor connected to the Displayport of the motherboard for years without issue.
When the monitor was replaced with a HP Z38c curved monitor it has issues when connected using a Displayport cable, but not when connected using HDMI. The problem with using HDMI is that it is limited to 30Hz refresh rate, rather than the native 60Hz that is available using a Displayport cable. The issue shows itself as the screen regularly "blacking out" for a second or so, and with horizontal lines "flashing". Sometimes, it might not happen for an hour or so, other times it might happen continuously over a short period of time.
The monitor has been replaced THREE times and all monitors have exhibited the same issue, so it doesn't appear to be a monitor hardware issue!
I have the latest Intel HD Graphics 630 driver installed (dated July) and the HP monitor information file. I have tried 3 different Displayport cables, three different power cables and have also installed a Geforce GTX 980 dedicated graphics card, but got the same issue.
The current Displayport cable I am using is brand new and is 8K compatible @ 60Hz and 4K @ 144Hz, which is far in excess of what the monitor requires.
The HP engineer seemed to think the issue was likely to be with the onboard graphics, given it works with an HDMI cable (at readuced refresh rate). I'm not so sure, but I really am at a loss as to what to do next to troubleshoot this issue.
Is it possible there are some "settings" relating to this motherboard and the use of Displayport that need to be changed? A long shot I know!