r375 Sky anomaly in NJMA when using a camera view

[Enjay]

I just noticed a minor rendering anomaly in my Marine Assault when playing with GZdoom. This is in the latest SVN but it goes back at least as far as the official release version. I have never noticed it before though so, as it is only visible at the edge of the screen, perhaps it can only be seen in widescreen modes?

WAD
http://www.doomworld.com/idgames/index.php?id=12214

Start the WAD, skip the briefing and then puke script 7.

Here is how it looks in Zdoom (screenshot size reduced to comply with the "640" forum rule).

See the very top left of the screen? It looks fine.

Now look at the same scene in GZdoom

See how there is an area that almost looks misaligned or something? In game, this moves and "shimmers" slightly making the effect more obvious. I notice that the edge of the anomaly lines up with some of the level architecture so that may be relevant. The sky itself is a constructed skybox.

If I go and actually stand at that point in the level, I don't see the effect (ie, it looks fine).

[Graf Zahl]

I'm sorry but I can't do anything here. This looks like a driver bug that just happens to be triggered by this specific situation. If I only change one thing about the camera it goes away.