Steps to repro:
1. Create new project > hierarchy > right click > 3d Object > plane
2. Select the ‘Directional Light’ > set resolution property to low resolution
3. Shadow Type to ‘Soft shadows’ from inspector window
4. Observe the Plane texture in Scene view and game view.

Note:
Occurs while creating a new project

Reproducible on:
2018.1.0b9, 2018.1.0b8, 2018.1.0b7, 2018.1.0b6, 2018.1.0b5

Works fine on:
2018.1.0b2, 2018.1.0b1, 2018.1.0a3, 2018.1.0a2, 2018.1.0a1, 2017.3.f3, 2017.3.f2, 2017.3.f1.

Frequency:
Always.

Environment:
Occurs on Mac and Windows