[LE] Black triangles after merging

[Krieger156]

So, I'm trying to merge black mage hood with black robes.

At NifSkopes, it looks fine, but when I tried running it on game, it came out like, large giant triangle spikes like if the mesh are completely broken/made into spiky like mesh.

Any ideas how to make it work?

 

Also while asking, do you guys also know how to merge armor mods to vanilla? In their perspective place ofc. Like mask mod+hood mod for example