Steps to reproduce:
1. Open the attached “IN-147819” Project
2. In the Assets folder, open “testscene”
3. Enter Play mode
4. In the Assets folder find “DummyMono.cs” and edit any comment to trigger a reload
5. Open “Sub Scene1” while being in Play mode
6. Observe the console
Actual result: After a script reload, Sub scene1 GameObject becomes "(Duplicate Scene)" and throws a MissingReferenceException that blocks all scene loading until restart
Expected result: Sub scene1 loads normally after a script reload, with no exceptions
Reproducible with: 6000.5.3f1, 6000.5.4f1
Not reproducible with: 1.4.7 (6000.3.20f1), 6000.5.2f1, 6000.6.0b4, 6000.7.0a2
Reproducible on: macOS 26.5 (M1), Windows 11 (By reporter)
Not reproducible on: No other environments tested
Notes:
- Bug does not repro with Hierarchy V2 on the 6000.5.X stream
- This error blocks all scene loading until Editor restart