According to some other topics about "invalid ClientID" when opening Ban-List.
If you ban users and they get deleted from the client/client_properties table through pruning, they remain in ban-list and those the above error.
It would be nice, that when the server is pruning old users (guests), they could be removed from the ban-list too, so you havent to do it manually by looking in the database which accounts are deleted.
Thanks.