Steps to reproduce:
1. Open the attached project (case_1207230.zip)
2. Select the "Zoo" Game Object in the Hierarchy
3. Add "Dog" to the Serialized Property table by clicking the little plus icon under it
4. Highlight the newly created entry and remove it by clicking the minus icon
5. Repeat Step 3 but select any of the other two options

Expected result: Depending on the selection, either "catto" or "mouso" is added to the table
Actual result: "doggo" is added to the table

Reproduced in: 2019.3.0f5, 2020.1.0a19
Cannot test in: 2017.4.36f1, 2018.4.15f1, 2019.2.18f1 (SerializeReference attribute not available)

Note:
- "Generating diff of this object for undo because the type tree changed" error is outputted to the Console on each action. See case 1198546.