How to reproduce:
1. Open the attached “Shadow_Casting_Regression“ project
2. Open the “Map” scene (Assets/Scenes)
3. Enter Play mode
4. Exit Play mode
5. Navigate to Assets/Test
6. In the project tab, right click and select Reimport
7. Observe the Scene view

Expected result: Shadows are cast by structures in the scene
Actual result: Structures do not cast shadows

Reproducible with: 6000.2.0a9, 6000.2.0b2, 6000.2.2f1, 6000.3.0a2 (macOS)
Not reproducible with: 6000.0.56f1, 6000.2.0a8, 6000.3.0a6
Fixed in: 6000.3.0a1 (Windows 11), 6000.3.0a3 (macOS)

Reproducible on: Windows 11, macOS Sequoia 15.6 (M1)
Not reproducible on: No other environments tested