Reproduction steps:
1. Open the project in "MemLeakTestV3.zip"
2. Select Memory in Profiler and enter Play Mode
3. Notice some memory has been allocated for Audio/Animation clips
4. Open scene "Empty"
5. Enter and Exit Play Mode
6. Notice that memory allocated in step 2 has now been deallocated
7. Go back to "SampleScene" and modify "New Timeline" asset
8. Repeat steps 2-5

Expected result: memory will be deallocated
Actual result: memory stays allocated

Reproducible with: 2018.4.13f1, 2019.2.14f1, 2019.3.0b12, 2020.1.0a14
Could not test with: 2017.4.35f1 (memory would always stay allocated), 2020.1.a15 (seems to have some issues with Playable Director)

Notes:
1. If you reproduce the bug at least once it will always reproduce, no matter what changes you make with the Timeline Asset. The way to restore it is to delete Library folder
2. Make sure that Hierarchy window is selected when you are viewing the Profiler stats as it seems to influence the results in some cases
3. Earlier versions might require you to recreate the entire setup since they do not support the new Timeline Asset
4. Issue is reproducible with any Timelines (not only the ones containing Audio only)
5. Bug sometimes may not reproduce the project is upgraded to another version