1. Open the attached “ReproProject”
2. Open the Addessables Groups window (Window → Asset Management → Addressables → Groups)
3. Select Build → New Build → Default Script Build
4. Select the “Play Mode Script” dropdown menu and choose “Use Existing Build”
5. Open the “InitScene” (Assets/Scenes/InitScene)
6. Enter Play mode
7. Click the “Spawn Blue” button and observe the Console
8. Click the “Spawn Red” button and observe the Console

Expected result: No errors are shown and both panels are instantiated
Actual result: The red panel fails to instantiate and error messages are shown

Reproducible in: 6000.0.11f1
Could not test with: 2021.3.40f1, 2022.3.38f1 (Missing UI Toolkit features)

Reproducible on: Windows 11, macOS 14.5 (Silicon)
Not reproducible on: No other environments tested

Notes:
* The issue does not reproduce if “Red” is replaced by “Red2” in “ScriptableObjects/Mapping”. “Red” uses UxmlTraits, "Red2" uses UxmlSerializedData
* Not reproducible in Player