Steps to reproduce:
1) Open the attached project.
2) Open scene 'main'.
3) In the Lighting tab, press 'Build'.

- The scene consists of three cubes and a plane. The big cube and the surface both are static, the two small cubes are not.
- The shadow cast by the big static cube does not mix properly with the shadows of the small cubes - they overlap with each other, creating dark areas (see image).
- In 'Directional Specular' mode, the small cubes cast no shadows.
- In 'Directional' mode, the shadows of the static and dynamic cubes overlap, resulting in dark areas, the same goes for 'Non-Directional' mode.
- 5.4.0b21 fails to bake in any other mode than 'Directional Specular', resulting in multiple "'Bake Runtime' job failed with error code: 5 ('Failed reading Bake Input System file.')." error messages, older versions build without errors, however, the issue still exists. If baked with an older version and switched back to 5.4.0b21 and then baked to 'Directional Specular' again, when changing the shadow Strength of the 'Directional Light', the shadow of the static gets darker when the shadow Strength is reduced (acts the opposite to how it should).