Every Adrenalin 18.x.x driver has the same issue for me which is triggered by running Fallout 4 :
Play the game, exit the game, the desktop on the primary monitor become desynced after about 10 to 45 seconds after existing the game. Basically the image isn't stable and it generally looks like every few rows is shifted about 50 pixels to the right.
I've boiled down the driver settings to be as stock as possible, basically enabling FRTC because FO4 needs vsync to be disabled, and making sure a few other settings are set right :
Driver global setting has Enhanced Sync enabled, FRTC enabled (either 60 or 143 FPS)
Game settings has FRTC enabled (inheriting from global settings), AMD Freesync set to 'AMD optimized'
Fallout4 has a manual .ini edit to disable VSYNC, which is required to get freesync working in this game.
Everything works as expected on the 17.12.1 drivers. Anything newer and it all falls apart.
Ryzen 1800X on ASUS C6H motherboard
Sapphire RX Vega 64 (the air cooled reference model)
Two Nixeus EDG-27 144Hz freesync gaming monitors both using displayport
Windows 10 Pro with all the latest updates, latest AMD chipset drivers, and latest ASUS motherboard bios.