Reproduction steps:
1. Open the attached “BugRepro” project
2. Open the “Assets/Test Scene.unity” Scene
3. Select the “Test” GameObject in the Hierarchy window
4. Right-click on the “I Have Custom Flag In Context Menu” component in the Inspector window
5. Select the “Custom Flag” item from the context menu
6. Observe the Console window

Expected result: "Custom Flag: 0" or "Custom Flag: 1" is returned
Actual result: Empty string is returned

Reproducible with: 2023.2.0a17, 2023.2.11f1, 2023.3.0b8
Not reproducible with: 2021.3.35f1, 2022.3.20f1, 2023.2.0a16

Reproducible on: Windows 11
Not reproducible on: No other environment tested