How to reproduce:
1. Open the attached project "TimelineCopyPasteBugReport.zip"
2. Open Window > Sequencing > Timeline
3. Open Tools > "ClipChecker"
4. Open any Scene in the Scenes folder
5. Lock the Timeline window and copy the Animation Track
6. Open a different Scene and paste in the Animation Track in the Timeline window

Expected result: The Animation Track is successfully copied over to a different Scene
Actual result: The copied Animation Track loses its properties

Reproducible with: 1.2.18 (2019.4.33f1), 1.4.8 (2020.3.24f1), 1.6.3 (2021.2.5f1), 1.7.0-pre.1 (2019.4.33f1, 2020.3.24f1, 2021.2.5f1, 2022.1.0b1)

Notes:
- The workaround is located in the "ClipChecker" script (Assets > Editor) which activates when the "WorkAround" button is pressed in the "ClipChecker" window, which sets the hideFlag of the "AnimationClipPlayable" asset to "HideFlags.DontSave" before loading the scene
- Not reproducible when pasting the Animation Track in the same scene