Reproduction steps:
1. Open the attached “BugRepro” project
2. Open the “Assets/Scenes/SampleScene.unity” Scene
3. Select the “Testing” GameObject in the Hierarchy window
4. Set the function to GameObejct.SetActive in the Inspector window
5. Select the “Testing (1)” GameObject in the Hierarchy window
6. Set the function to Light.enabled in the Inspector window
7. Select both the “Testing” and “Testing (1)“ GameObjects in the Hierarchy window
8. Select any of the “Testing” or “Testing (1)“ GameObjects in the Hierarchy window
9. Observe the Inspector window

Expected result: The function that was set remains unchanged
Actual result: The function is reset to “No function”

Reproducible with: 2022.3.14f1, 2022.3.23f1, 2023.1.20f1
Not reproducible with: 2021.3.36f1, 2022.3.13f1, 2023.1.19f1, 2023.2.0a1, 2023.2.17f1, 6000.0.0b14

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