Steps to reproduce:

1. Download the attached project and open the TestScene01
2. Navigate to the Lighting Settings and make sure that Realtime Global Illumination is enabled
3. In the Lighting Settings window, click on Generate Lighting
4. Once the lighting has been baked, navigate back to the Lighting Settings window and toggle between different Environment Lighting Source options
5. Observe the artifacts on the one-sided plane

Notes:

- Affects all ambient color modes such as: color, gradient, skybox (both procedural and HDR)
- Only occurs when Realtime GI is enabled
- Also occurs when Is Transparent tag is enabled and when Double Sided GI is enabled in the material settings