Before this gets thrown into the bug section, this is not a bug I am asking Bethesda about, this is a bug I'm trying to solve with modding, and thus need modder assistance, not bug hunter assistance.

At the moment the Dawnguard sleeveless armor only uses the _1 mesh, thus it is at max scale all the time. For some reason it is refusing to recognize that the _0 mesh exists, but I can't figure out why exactly.

Inside the _0 nif file the records weren't in the exact same order as in the _1 mesh, so I put them in the same order, but that didn't solve the issue (it does sometimes with other meshes with similar issues).

Any other modders with more experience with these types of meshes have any ideas, because I'd like to fix this without having to wait and see if someone else does?

Are they in the exact same directory? It wouldn't work if they were in different folders. That's the only thing I can think of.

Yep same directory. Everything seems the same across both files, same amount of vertices, same order etc, but it just doesn't work.

The files in question are: dawnguardbody3m_1.nif & dawnguardbody3m_0.nif

From Dawnguard.bsa > meshes\dlc01\armor\Dawnguard\

Is it possible that the two nif files aren't physically different? I'm assuming you already compared them in Nifskope or something similar, but I guess you never know?

Have you opened them in nifskope to verify there's a difference and they didn't just use one mesh named twice?

Ok so the problem doesn't seem to have been the meshes... it seems that a mod I made to fix the fact that this armour doesn't have a 1st person mesh (and thus clips into view in 1st person) caused this issue.

How... I have no freaking idea. All I did was point the armor addon record for this armor to the iron cuirass 1st person mesh. That shouldn't have caused this issue, at all...

I wonder if it is related to all the errors you get loading the Dawnguard.esm...