[1.12.2] 3D Armor texture not fitting and armor is backwards in inventory

Currently trying to redo my armor to fix this bug: https://github.com/itsmeow/betteranimalsplus/issues/31

But the texturemap isn't fitting on the actual 3d piece.

I've got the item here: https://github.com/itsmeow/betteranimalsplus/blob/master/src/main/java/its_meow/betteranimalsplus/common/item/ItemHirschgeistSkullWearable.java

with the texture defined inside.

I've got the model here https://github.com/itsmeow/betteranimalsplus/blob/master/src/main/java/its_meow/betteranimalsplus/client/model/ModelHirschgeistHelmet.java

(SkullArmorPiece in the same folder is our old one)

And yet, the armor texture is still not fitting (and I think the bug still persists, any reason why it happens in the first place)? I've currently got the raw texturemap as the layer 1 and the real texture as layer 2 and it just doesn't fit

See here for textures: https://github.com/itsmeow/betteranimalsplus/tree/master/src/main/resources/assets/betteranimalsplus/textures/models/armor

Also, I think the original bug was because the head itself wasn't a child of bipedHead, but copied its rotation values and something about that is weird in the inventory renderer.

But I'm still not sure because I've seen it like once with the new one. Also, the original bug does not ALWAYS happen in the inventory but instead when the player is at some specific rotations.

By "not fit" I mean it's completely off (and I can't pinpoint the texture position, it seems to be jumbled all around)

Basically:

Why doesn't the texture fit?

Is there a proper fix to this backwards inventory bug?

How should the texture/model be exported from Tabula to make it correct?