How to reproduce:
1. Create and open a new project
2. In the Hierarchy, create any 3D object (ex. cube)
3. In the Inspector, Mesh Renderer component, expand Materials property
4. Click the target button to change the material
5. Select any material from the window
6. Notice the material has changed in the field and in Scene/Game view
7. Select a different material
8. Observe the field and Scene/Game view

Actual result: The material remains the same as selected in step 5 both in the property field and visually in the Game/Scene view
Expected result: The material changes each time a different material is selected

Reproducible with: 6000.5.0b9, 6000.6.0a2, 6000.6.0a5
Not reproducible with: 6000.0.75f1, 6000.3.16f1, 6000.4.8f1, 6000.6.0a1 (b0e692525f04)

Reproducible on: macOS 26.4 (M1 Pro)
Not reproducible on: No other environment tested

Notes:
- The material does not change even when double click selecting from the Select Material window
- Other similar menus do not appear to be affected