Baking by Mesh name doesn't work. Unwanted artifacts on part of mesh that should not be baked.

I'm using a low poly mesh from blender that is correctly UVED ( No overlapping UV's as seen in the picture)

I have separated the main mesh into three meshes. I only want ONE of those meshes to be baked by another, high poly mesh.

I only want the main skull to be baked as seen in the image. I DONT want the teeth or the " leather" straps, ( the flat strap-like mesh on the back) to be baked.

I export those three meshes together to a FBX file and then into Substance painter.

I then  select my high poly mesh in substance and check " By mesh name" in the baking options.

However when baking there are artifacts all over the place. I thought this method was literally designed to circumvent this? I can't understand what I've done wrong. I've paid attention to the case sensitive suffixed _low and _high. Only the spesific mesh I want to bake has the suffix. And only the specific mesh i want to bake has a high poly variant. The two other meshes has no suffix and no high poly variant. They're completey isolated. So why does substance insist on baking OVER these meshes with artifacts?