There are both SNOW flats and textures

[Liliam]

This one is bound to get a critical fix, I'm sure...

There are both a set of SNOW01, SNOW02 and SNOW03 flats and a set of textures with the exact same name. The flats come first in the IWAD, which means if you try to make a multi-patch texture using any of these, it'll find the flats first and crash the game when the texture tries to load.

There might be other duplicate lump names somewhere in there, I haven't really checked.

 

[K.S.]

This is one of those unfortunate things that we can't really fix without completely overwriting the IWAD, which is something that we're aiming to avoid for obvious reasons...