I made a mod which replaces the default faces with the Head06 model by Throttlekitty so that NPCs will use it as well, but I've noticed a weird glitch in-game:

http://i.imgur.com/QqsqO.jpg

On about half the NPCs I encounter, seemingly without rhyme or reason, they seem to be rendering with a vanilla normal map instead of the one that fits the Head06 UV map. You can see in my screenshot, on the Imperial on the right, she has eyelids on her cheeks, and a second set of nostrils underneath her nose. But on the Imperial on the right, there's no problem. Both screenshots were taken in the same sitting, and no mod changes were made between shots. It doesn't appear to be related to the age sliders in any way, as I can make a player character of any age/race with no problems, it's just the NPCs.

As far as I know, I'm not using any other mods that edit the races in any way, though I am using Tamriel Immersion Experience which edits individual NPC faces, and even on a new game the issue persists. I haven't been able to find anything else about this problem online, which is why I came here.

So, does anyone have any ideas?