Found a strange bug outside of Upsilon

[Romulator]

Sounds like a graphical issue that has been spoken about here: https://www.frictionalgames.com/forum/thread-30680.html

In that same thread, nebej suggests this as a fix.

You could try a temporary manual solution if you would like
Rename the undergrowth folder in the game folder to _undergrowth. This will disable rendering of the terrain vegetation (which it looks like is the problem)