Issues with transparency on the eyes mesh

[iz-Moff]

Hi. Does anyone here have experience with editing eye meshes? 

I can import the default eye mesh (eyesfemale.nif), move the vertices around, then export it, and that works fine.

However, if i try to create a new mesh for the eyeballs, the parts of the eyeball that are supposed to be behind the semi-transparent bits are not displayed properly, particularly the part behind the strip of polygons underneath the upper eyelid meant to simulate some shading going on there.

Here's what i mean:

All i did in Blender was that i imported a properly working .nif file, went to edit mode, selected vertices that make up the right eyeball, duplicated them, and then deleted the original vertices, that's it.

You'd think the eyes should look identical, but nope, whereas on the left eye these shadow polygons are drawn as expected, the right one just clips part of the eyeball.

And i have no idea why that happens. I'm guessing that individual vertices must have some sort of property on them that determines how they interact with transparency, but i have no idea where could this information be stored in Blender, and why is it not getting preserved even if original vertices get duplicated?

Does anyone have any ideas?

 

p.s. i'm using nifly plugin to import\export .nif files.

 

I'll also attach an archive containing examples of working and glitched .nif files. def.nif looks the way it should, edited.nif shows the issue on the screenshot above. They both look identical in Blender, and i tried inspecting them using NifSkope and couldn't find any difference besides the order of vertices.

files.zip