How to reproduce:
1. Open the attached project "2DBug.zip"
2. Open Assets/Scenes/SampleScene.unity
3. Open Window>Animation>Animator
4. Select "Character" in the Hierarchy window
5. Select any transition in the Animator window
6. Play the preview animation
Expected results: The preview plays both the first and second animation
Actual results: The preview plays only the first animation
Reproducible with: 2021.3.33f1, 2022.3.14f1, 2023.2.2f1, 2023.3.0a16
Reproducible on: Windows 10 22H2
Not reproducible on: No other environment tested