This could be a texture error if you are using a normal map maybe, i’ve had similar problems before, here’s how i fixed them if it wasnt the normal map!
This does depend on the geometry of your mesh a bit but has worked for me a few times when i got stuck…
Try exporting tangent spaces and/or loose edges depending on the mesh or just exporting normally and importing with the “Import Normals” or “Import normals and tangents” option… here are a couple of screenshots!
Export:
Import:
