I found that sometimes, without any specific preconditions, the world geometry will not draw.
Boxes, doors, lights, enemies or other props will draw as normal.
The geometry is still colliding as normal, so you can walk on thin air and not fall through the world.
I found two occurences thusfar, one occurence in the area where "Alien Artifact 2" is located and one occurence after switching on the furnace, while I was in the elevator going down, the elevator walls weren't drawn.
Going through a door into a different area and back has resolved the issue.
If it happens again I'll try to capture a video for clarification.