“InvalidOperationException” errors are thrown when entering Play Mode in the Timeline’s Customization Samples

Unity: Timeline (Core)

6.6.X

6.5.X

6.4.X

6.3.X

6.0.X

6.7.X

6000.7.0a2

Steps to reproduce:

Create a new Unity using the Universal 3D template
Open the Package Manager (Window > Package Management > Package Manager)
Select the Timeline package
Open the Samples tab
Import the "Customization Samples" Sample
Open the "Assets/Samples/Timeline/1.8.12/Customization Samples/Demo/Scenes/Timeline_CustomTracks.unity" Scene
Enter Play Mode
Observe the Console window

Actual results: “InvalidOperationException” errors are thrown

Expected results: No errors are thrown

Reproducible with versions: 6000.0.75f1, 6000.3.16f1, 6000.4.8f1, 6000.5.0b9, 6000.6.0a5

Tested on (OS): MacOS Silicon Tahoe 26.3, Ubuntu 24.04