Reproduction steps:
1. Open the attached “IN-108816” project
2. Select “test/matC” Material in the Project window
3. Select “Flatten Material Variant” option from the Inspector window’s context menu
4. Repeat steps 2-3 with “test/matD” material
5. Restart the Editor
6. Drag “test/matB” Material onto “test/matC” Material
7. Drag “test/matB” Material onto “test/matD” Material
OR
1. Open the attached “IN-108816” project
2. Flatten the materials and unload unused assets (Tools > Test Material Bug part1)
3. Assign “matB” Material as parent of “matC” Material (Tools > Test Material Bug part2)
4. Assign “matB” Material as parent of “matD” Material (Tools > Test Material Bug part3)
Expected result: Both “matC” and “matD” materials keep their properties
Actual result: “matC” material properties are reset while “matD” material properties are preserved
Reproducible with: 6000.0.75f1, 6000.3.16f1, 6000.4.8f1, 6000.5.0b9, 6000.6.0a5
Reproducible on: Ubuntu 25.04, Windows 11
Not reproducible on: No other environment tested