Incorrect Shading On Objects Using World Position Offset And Rotate About Axis

When using the rotate about axis node and WPO to move the vertices of an object to always face the player this seems to introduce some shading errors with any light (except skylight).

1. Open attached project
2. Move around the meshes in the scene so that they rotate in place
3. (Optional) rotate the directional light along the z-axis

RESULT
The objects will be lit incorrectly at some angles or cast incorrect self shadows. The effect is more obvious from different directional lighting angles.

EXPECTED
The objects rotate to face the camera and are lit correctly according to the directional light's rotation.