How to reproduce:
1. Create a new Unity project
2. Create a new UI Dropdown GameObject
3. Create a Prefab from this dropdown by dragging it into the Project window
4. Select the dropdown instance in the Hierarchy window and change some property
5. Open the Prefab overrides dropdown and select the Dropdown component
6. After it has been selected, select the parent Prefab object and re-select the Dropdown Component

Expected result: no errors are thrown
Actual result: multiple exceptions are thrown

Reproducible with: 2018.4.31f1, 2019.4.19f1, 2020.2.2f1, 2021.1.0b3, 2021.2.0a2

Errors:
NullReferenceException: SerializedObject of SerializedProperty has been Disposed.
GUI Error: You are pushing more GUIClips than you are popping. Make sure they are balanced.