That is pretty weird. Are you sure that the normals are working and the green channel is inverted? If the diffuse, normal and masks are fine, there may be something with your mesh.
Gotcha. Was curious if it were even possible to do that with decals. Like have just a normal map by itself with no diffuse or anything and have it projected.
Considering it's diffuse only with ambient light I think it looks great :) Love the metallic specular highlights and the scratches are really well painted