Issues with eyes dissapearing behind transparent objects.

[OGY]

I've been working on converting an armour over from Fallout 4; I've been pretty successful for the most part even with it being my first time doing it, but no matter what I do I can't get the characters' eyes to stay visible through the transparent helmet glass. I've tried basically porting over the settings from similar transparent objects, like various glasses mods, but I've had no luck in finding what exactly causes the issue or how to fix it. Curious thing is, a handful of eyes from one or two packs do stay visible, but I don't want to have some kind of system where the helmet's only useable with one set of eyes or another.