Okay I tried re-importing, I did have “compute normals” checked before but I tried importing the normals and tangents this time and appear to be getting the same result:
I am setting up my normals using a master material and then adding the normal map to the instance. I noticed I see the same shadow issue whether I add my own normalmap or use the default set up here:
For reference I baked the normalmap in Blender baking from high-res (multi-res modifier 3) to low res