I get random texture errors with the latest official version of GZDoom, it just looks like the "Disable Textures" mode is used for several parts of the map and randomly switches on and off depending on the angle and distance I am standing relative to these "texture-less" structures:
It seems to occure more often on
Additive translucent mid textures
Floor and ceiling mirrors
Sectors seen through portals
Skyboxes
Horizon lines
I have a nVidia Geforce 8500 gfx card with the latest stable drivers from the official nvidia page. If you need anything more, just ask.[/list]