ID 372021 - Black splotches/artifacts in highlights on AVP with principled material

Problem summary
Black splotches/artifacts in highlights on AVP with principled material. This occurs when a normal map is applied to the mesh. 

Customer reported version
modo.12.1v1

Customer reported platform
windows10

Steps to reproduce
1) Open Modo.
2) Select file>open and open the attached scene.
3) Switch the viewport style to "advanced."
4) Compare the left sphere (Physically based shading model) to the right sphere (Principled shading model).
Result: The principled material has black/dark splotches in the highlights towards the edges.

Workaround
Unknown. 

Reproduced by support
This bug has been reproduced in:
12.1v1 - Windows 10, OSX 10.13.5
12.0v1 - Windows 10
11.2v3 - Windows 10
11.2v1 - Windows 10, OSX 10.13.5

Earliest version tested
11.2v1 - Windows 10, OSX 10.13.5 - This feature did not exist before this version

Expected behaviour
Each shading model should render without artifacts in the Advanced viewport (AVP), even with a normal map applied.

Actual behaviour
The principled shading model on a material renders with artifacts in the AVP.