This started with the game's november update. I had an R9 Fury back then and it's still the same with Vega 56.
Happening with the 18.11.x, 18.12.x and the new 19.1.x drivers.
VGA: RX Vega56
RAM: 16 GB DDR3
OS: W10 1809 latest version
I also reported it to the devs since it was a game update that broke it Graphics issue with the terrain surface after the November Update