Mostly because 3DC tends to delete too much (or changes their values) especially with borders that're close to each other. Example with the mouth area of the default head:
Unity default PBR shader uses a particular layout for glossiness. It has to be stored in a specific color channel. It could be your Shader Forge shader expects the same?
the engine can't read or open the mesh, hence reverting to a default mesh, which is a sphere. can you post a screenshot, exportlog and the asset path that the entity is linking to?
This is "only" a UI limitation. You can edit 3ds Max\Macroscripts\Macro_BakeTextures.mcr Look for "padding" and change the range to [0,256,2] or whatever (min,max,default) and save.
I tried a couple of re-renders using your suggestions... This is using scanline renderer, default lighting, and materials as per your request. Is this what you meant?
already done ^^ but 128 should be enough no ? it was 32 by default .. this is weird because when I Unlit there is no seam noticeable just when light is on in interior this is just bad :( (