Steps to reproduce:

1. Create and open an empty project.
2. Download and add the attached component 'TestClass.cs' to a game object.
3. Add 2 or more items to the 'Unity Event ()' serialized property of the Test Class component.
4. Remove all the items.
5. Add the items again.
6. Remove the items again.

Actual results: Several errors are thrown in the console and the items don't get removed properly.

Expected results: No errors are thrown and an item is removed when you press the minus button.

Reproducible with versions: 
6000.0.5f1
2023.2.0a10

Not reproducible with versions: 
2022.3.29f1
2021.3.38f1

Tested on (OS): MacOS (M1) 14.4.1