How to reproduce it:
1. Open user's attached project
2. Load 'SampleScene' from 'Assets' > 'Scenes' folder
3. Hit 'Play'
4. In the Game view observe an animation
5. Hit 'Pause'
6. In the Hierarchy view find 'Root' prefab and enter Prefab mode
7. Leave the Prefab mode
8. Hit 'Play'
9. Observe errors in the Console window

Expected result: In the Game view animation starts playing
Actual result: Animation doesn't start, and errors occur in the console window

Reproducible with: 2019.4.0f1, 2019.4.11f1, 2020.1.6f1, 2020.2.0b2
Could not test with: 2018.4.27f1 (animation doesn't work)

Note: To work around this issue, you have to reimport 'Root' prefab