I already posted this on the game's Steam Discussions page. And a developer responded with:
"This is a problem on certain Radeon cards, but we don't know why unfortunately. It may be caused by a bug with the baked lightmaps and the way Radeon cards renders them. If it is caused by the lightmap it makes sense that it gets worse with lower graphics. Some have reported that it may help to turn off "reflections."
Ryzen 7 1700X @3.791GHz (stable)
GIGABYTE GA-AB350M-Gaming 3 (Rev. 1.0)
XPG GAMMIX D10 16GB (2x8G) DDR4 3200 (auto speed stable)
Windows 10 Pro x64 Version 1803
Radeon Software Adrenalin 2019 Edition 19.1.2
1080p-59Hz (no 60 available) very high/maximum (VSYNC, all enabled): Game configuration is fine, game starts fine, gameplay starts fine, but is soon met with unrendered/black surfaces. This varies depending on the area/angle.I changed a few antialiasing/other one below or above it, and now everything's black. But restarting the game returns to normal for a short while.
1080-59 very high (no sync): Same, maybe 5% less often.
1080-59 high (VSYNC, all enabled): Much less unrendering.
1080-59 high (no sync): Much less unrendering, less often.
1080-59 medium (VSYNC, all enabled): Even less unrendering.
1080-59 medium (no sync): Same as above.
1080-59 low (VSYNC, all enabled): THE MOST UNRENDERING!
1080-59 low (no sync): NO CHANGE FROM ABOVE!
1080-59 lowest (VSYNC, all disabled): No problems most of the time, except sometimes in the original house moving the camera through the walls.
Screenshots attached (problem, normal, problem). I was told that it uses Direct3D (store page says DirectX 11).
