To reproduce:
1. Open up users attached project
2. Go into Window > Asset Management > Addressables > Groups
3. Make sure 'GameObject.prefab' label 'extra label' is check-marked in Labels
4. Click Manage Labels in Labels options and remove 'extra label'
5. Exit out this current Manage Labels window and go back to Adressables Groups window
6. Notice that there is no current label selected for the 'GameObject.prefab'
7. Go back to Manage Labels and add 'extra label' as a label to 'GameObject.prefab' again

Expected result: 'extra label' was deleted beforehand so when added back it has no check-mark
Actual result: When added back in 'extra label' retains its old check-marked state

Reproduced in: Version 1.3.3 (2019.3.7f1), Version 1.8.3 (2018.4.22f1, 2019.3.7f1, 2020.2.0a9)
Could not test with: 2020.1.0b7 (Version 1.8.3, 1.7.5, 1.3.3) due to another bug happening and not allowing me to use Manage Labels window