As you can see from the first two pictures, it flickers up and down (occasionally going off the screen if you look at it from the right angle XD).
And yup, exact same place, right along the shadow line, and an extra square meter beside that where there isn't any shadow.
This also happens in Front Runner (another DF2 quickie port), which uses the same map, but just a different part of the map so I didn't see it back when I first tested Front Runner.
Anyways, I'm gonna go see if I can get it to stop happening by heading to the _c.tga...
Edit: It is not the color map. XD