Shading errors that only appear in renderer

aaeriam

Working on a gun model right now. Loaded the high and low poly into substance, baked by mesh name, and everything looks fine until I open the renderer in substance and marmo. Not sure if the error is caused by the topology or the baking or if it's something else that I'm missing. 

EarthQuake

In Toolbag, make sure the tangent space (found in the mesh properties) is consistent, I believe Substance uses Mikkt. You can set a default TS in Edit-> Preferences, this will apply to newly imported meshes but not the meshes currently in your scene.

Try exporting a 16bit normal map as well, I'm not sure if Substance uses dithering with 8bit files, if not that can cause banding.

It looks like your mesh normals are rather extreme on the lowpoly too, which can cause problems. Generally for an asset like this you would want to add hard edges at the UV seams so the normal map doesn't have to do as much heavy lifting.