Testing procedure:
- Warp to any map.
- Type "IDBEHOLDI" to get the blur sphere powerup.
- Save the game.
- Load the save. If "Screen wipe style" is set to "Crossfade", a rendering artifact will appear on the screen while the crossfade is happening. For me, it appears in the bottom area of the screen and looks like a thin black column spanning about 1/3 of the screen height.

Git bisect shows that the issue started happening in this commit.
System information: NVIDIA GTX 660, Windows 7 64-bit.