I've got a Sapphire Pulse Radeon RX 590. I try to connect it via DisplayPort with my DELL monitor. But every 5 to 60 seconds I have got a blackout on the display. It's really only the display, as the content in a game or just desktop activities is going on. Also the menu of the display disappears, so it is like resyncing. Same for both DP outputs. With HDMI no trouble, but less accurate pictures (e.g. only 8 bit color depth).
Newest drivers installed, factory settings restored and played with the output parameters, without success.