I got a new monitor the other day (LG 27UD59-W) but ran into issues when trying to play games in 4k. Videos in 4k work just fine, but games (so far tested Rocket League, Counter Strike Global Offensive and Stellaris) all have issues in 4k where either the monitor loses connection entirely or the game either flickers to black repeatedly or turns black completely, while the game still keep going and reacts to input. To get the monitor responding again I have to alt-tab and turn the monitor off and on again.
I read of a similar problem here before, but there the issue seemed to be with Displayport only. I have the same issue no matter if I use Displayport or HDMI.
I use the Radeon Driver version 19.12.3
I have a 8GB XFX Radeon RX 480 RS, an Intel Core i5 6600K 4x 3.50GHz and a 600 Watt be quiet! System Power 8 Non-Modular 80+ PSU.
If you need any more information let me know, I monitored the temperature of CPU and GPU during the incidents, but there didn't seem to be anything out of the ordinary.