Teach me how to solve my own dark face problem

[bathoz]

I've got the typical "dark texture over face" issue that seems to crop up every now and then. I did the usual things that are suggested on these and other forums, but it didn't help.

 

But then, in frustration, I looked to 'nuke it from orbit', reinstall everything and try again. Except, before I got there, I decided to disable every mod barring the graphical 'base' (LOD, wireframes and textures, not skeletons or bodies or anything).

 

And lo and behold, dark face gone.

 

From there I added and removed mods experimentally using Mod Organiser to work out which mod was at fault. It ended up being ZazExtension. Except, of course, it's not really Zaz (as reinstalling or trying different versions doesn't help).

 

Can someone show me how to find out what Zaz is messing with (or what is messing with Zaz) using the tools available?