Reproduction steps:
1. Create a new project
2. Window > Sequencing > Timeline
3. Select any GameObject and click "Create" button in the Timeline window
4. Add an Audio Track by pressing "+" button
5. Press "Show curves view" button
6. Select one of the Audio Track properties, right-click in the curves view and select "Add Key" option
7. Select a different Audio Track property and click on the Key selection area at the position where the key was added in the previously selected property
8. Observe the Console
Actual result: “ArgumentOutOfRangeException” and “GUI Error: Invalid GUILayout state in TimelineWindow view” errors are thrown
Expected result: No errors or warnings are thrown
Reproducible with: 6000.0.0f1, 6000.0.76f1, 6000.3.17f1, 6000.4.11f1, 6000.5.0b12, 6000.6.0a7
Reproduced on: Ubuntu 24.04, macOS Tahoe 26.5 (M4), Windows 11