Graphic Glitch - Grid of grey walls appearing

Bug Report # 1,756,831,913

Specs:
i7 6700K
GTX 970
32GB RAM
DX 12 installed, DX 11 used in game settings
Windows 10 Pro 64-bit
GeForce Driver 398.11

Game Graphics Settings:
Windowed Fullscreen
2560x1440
Water Detail High
Shadow Quality High
Antialiasing MSSA x4
Texture Quality High
Texture Filtering 8x Anistrophic
Lighting Quality High
Post Processing Enabled
Screen Shake Disabled
Multithreading Enabled
DX11

Map: Shaped Underground River

Depending on where I stand a grid of grey walls appears and disappears. Making them appear and disappear was completely reproducible just by walking around and standing in certain places.

Grid of grey walls:
https://imgur.com/uW1BG50


Area I had to stand in for them to appear:
https://imgur.com/CatvoQU


There were other a few other areas lower in the map that also caused a similar effect but they were much smaller spots, just a step or two's distance. There was an Abyss (no depths) in the map to the right of this area.