I faced this weird behavior inside my sharepoint on-premises 2013.
i have a sub-site which have a unique permission , and inside this sub-site i added a security group named "Network Members" and i grant it "Restricted interfaces for translate":-
then inside this sub-site i have a list, which also have a unique permission. and inside this list i added the same group "Network Members", grant it a Read permission:-
- finally i have a list item, which i define to have a unique permission, and inside the list item i added the "Network Members" and grant it a Contribute permission as follow:-
now i removed the "Network Members" group from the sub-site, as follow:-
But i have noted that the "Network members" group was also removed from the List and the related list items. so i am not sure if this is a bug. as when i add the security group to the sub-site it was not added to the list and list items, since each component have a unique permission. but why when i remove the security group from the sub-site it was removed from the list and list items.. now i can add back the security group to the list and the list items without having to add it first to the sub-site... so can anyone adivce how this is being handled?