Any idea what causes this graphic OR Mesh error?

[Hodvar]

I was working on a little editing, try to make a custom combat helmet for Fallout 3 by editing existing helm meshes. Simply add a chin strap from Vault Security Helmet to the Combat Helmet. I do the stuff on blender, seems no problem there. I export it with most common armor exporting setup and seems work (Looks different than everyone elses custom helm on Nifscope, it seen positioned directly to the head. I may do something wrong there, but its work in game anyway) in GECK screen without any problem. BUT, when I open the game and check the look of the helm I see some graphical errors on the helmet. In the Chin Strap location there is some kind of tearing or something like that as you can see in the image below. Any idea what causes this? Is there a blender or exporting error that I do (which Im think so but dont know where) or a simple graphical error of the game?

 

This happens all the race and sex, and Vault Security Helmet does not has same error.

 

Blender Looks; GECK Look:

In Game Looks :

[BaconModss]

Mate,firstly try seeing if you exported it well.Then,if the problem is still active,try seeing if you textured the strap well or if you did some mistake when adding the chin there.If the problem STILL appears,just try making the chin from the scratch again mate,I really don't see other solution than that :D