1. Move the mirrored shells +1 out of 0-1 space. Mudbox hates direct overlaps. 2. Not sure, but try subdividing it without smoothing and see if it helps.
Like rabbid said. Offset the mirrored uv islands out of the 0-1 uv space. After that import the model inside mudbox and create a paint layer and save the scene. After that go to where the project files and rename the textures located there like so texturename_u1_v1 texturename_u2_v1. After that open the scene again inside…
Background details: I made a model in ZBrush and polypainted it. Made a lowpoly and used Topo to bake the polypaint info to a texture and worked on it with photoshop. Later I got a portfolio review and was told to try taking the model into Mudbox 12 and paint directly on the lowpoly as the polypaint from ZBrush had gotten…