--> Use the Timeline package (minimum version 1.2.0) to reproduce the bug. <--

How to reproduce:
1. Open attached project "Case_1224184" and load the scene "SampleScene"
2. Click on "parent" prefab in the Hierarchy
3. Make sure the Timeline Window is visible on screen
4. Add a GameObject as a child to the prefab instance
5. In the Inspector for the Prefab instance click on Overrides and select "Apply All"

Reproducible in: 1.2.0 (2019.3.0a10), 1.3.0 (2019.3.4f1, 2020.1.0a26), preview.1 - 1.4.0 (2020.2.0a1)
Not reproducible with: 2017.4.37f1, 2018.4.18f1, 1.1.0 (2019.2.21f1)

First lines of the stack trace:
0x00007FF70E41D3C8 (Unity) ScriptingGetComponentsOfTypeFromGameObjectFastPath
0x00007FF70E6ABA27 (Unity) GameObject_CUSTOM_GetComponentFastPath
0x0000021AD065C29C (Mono JIT Code) (wrapper managed-to-native) UnityEngine.GameObject:GetComponentFastPath (UnityEngine.GameObject,System.Type,intptr)
0x0000021AD065C1B3 (Mono JIT Code) UnityEngine.GameObject:GetComponent<T_REF> ()
0x0000021AFAE5B9DB (Mono JIT Code) [D:\Projects\TimeLineCrash\Library\PackageCache\com.unity.timeline@1.3.0-preview.7\Runtime\Animation\AnimationTrack.cs:610] UnityEngine.Timeline.AnimationTrack:OnCreateClipPlayableGraph (UnityEngine.Playables.PlayableGraph,UnityEngine.GameObject,UnityEngine.Timeline.IntervalTree`1<UnityEngine.Timeline.RuntimeElement>)

Notes:
1. The "parent" prefab has a Playable Director that has a Timeline, which has a Control Track that sets the "child" prefab as a grandchild to the "parent" prefab. The "child" prefab has a Playable Director component with a Timeline that has an Animation Track set
2. If the Timeline window is not seen on screen, the crash does not occur