I created a model in another program, and imported it to Blender to map the UVs. Parts of the model are symmetrically flipped mesh planes. I noticed in Blender that the mirrored objects display as darker, and on further checking, I find that the face and vertex normals are in one direction and the "vertex-per-face" normals are opposite.
I've tried the Recalculate Outside and Flip Normals commands, but that just inverts them without unifying the direction. How can I flip JUST the "vertex-per-face" to get them all in the same direction, as they are in the original un-mirrored object that was copied?