I recently sculpted a character model from scratch in Mudbox, built the low-poly version by Quad Draw in Maya, unwrapped and cut the UV's into mirrored shells over multiple UV tiles, Baked the Normal maps from the sculpt through HandPlane, fully textured the model in Substance Painter, and brought those textures back into Maya.
Substance Painter does not support painting across UV tiles yet, so of course I have seams to cleanup, but I can't figure out how to get rid of them. The original baked normal map appears fine, but the Substance normal maps I painted on all have UV seams between tiles. I can't paint the seams out in Mudbox either. The flat normal map color will cover it, but if I try to use the clone stamp tool there is still a UV seam, so I'm wondering if the normals are somehow flipped at the edges only?