Since around patch 8.1 there is a pretty annoying bug that randomly cause parts of the UI to flicker (like parts of the map, icons, bars). From my personal testing i noticed that its caused by RivaTunerStatisticServer (RTSS) which im using to track my CPU/GPU usage/temps and display them on the screen like this: https ://i.imgur.com/2we7sBR.jpg
So far i noticed that this is happening only in DX12 and when the overlay is enabled. Turning it off stops the flickering.
At this point i tried pretty much everything - fresh windows, different drivers reinstalled with DDU, no addons, fresh game installation and even a new GPU.
A few examples here:
https ://i.imgur.com/a7XSUk1.mp4 flickering Icons
https ://i.imgur.com/hyrLoKb.mp4 flickering parts of the map
https ://i.imgur.com/NuL8uec.mp4 same issue
After playing on the SL beta i noticed that its happening there too. WoW Classic is not affected by this.