Had the same problem. You probably weight some of the vertices (the area where mesh showing up in front of other mesh) to more than 4 bones. The limit is 4 bones per vertex. So the area shown could've been weight to thigh, pelvis, spine, spine1, and skirt or something else. Do remove zero weight as well. You can see in Nifskope if it's fix or not. After that all I have to do in Nifskope is change the "Num UV Sets" from 1 to 4097, copy/paste bslightingshader, and update tangent space that's all. If the original mesh has vertex color then change "Has Vertex Color" from "no" to "yes" Also try the latest exporter 3.7.3. http://skyrim.nexusmods.com/downloads/file.php?id=5622