The translucent water at the map start is being rendered incorrectly. Depending on the angle, distance and height from the window the water will vanish and appear at different heights. It is hard to explain but it occurs in software mode. Maybe it is just the nodebuilder frakking up again, I do not know.

Inside:


Outside:

That's strange... the texture actually is controlled by the 3d floor

I actually managed to fix this somehow. There was a second 3D sector being stacked in there that must've been playing hell with it, as it seems to look okay now.

The second 3D floor stacked in was being used for an effect, but somebody kept breaking it by making it have volume, when it didn't actually any at all. Strangely, I had fixed this myself before, but then somebody else broke it again