Steps to reproduce:

1. Download and open the attached repro project (case_1348581-Lightmapper_NoShadows.zip)
2. Navigate to Lighting window
3. Make sure that either Progressive GPU or Progressive CPU lightmapper is selected
4. Generate lighting
5. Observe the differences between the baked output on 'factory - Shadows OFF' and 'factory - Shadows ON' GameObjects

Notes:

- Reproduces in: 2019.2.0a7, 2019.2.0b1, 2019.2.21f1, 2019.3.16f1, 2019.4.23f1, 2019.4.24f1, 2019.4.28f1, 2019.4.29f1, 2020.1.17f1, 2020.2.5f1, 2020.3.14f1, 2021.1.14f1, 2021.2.0b2, 2022.1.0a1
- Does not reproduce in: 2019.1.14f1, 2019.2.0a1, 2019.2.0a3, 2019.2.0a5, 2019.2.0a6
- Enlighten is not affected
- Setting Min and Max Bounces property to 1 results in flat uniform lighting on the 'factory - Shadows OFF' GameObject