I'm not sure if this is specific to group users, but there is a bug where the numFollowers and numFollowing isn't being updated properly. Going through the database I found users with multiple followers but not with the appropriate total number.
I imagine the issue is due to improper timing of operations (synchronization of critical section, ie follower counter). I've been making progress on fixing other similar issues on a branch.
I'm not sure if this is specific to group users, but there is a bug where the numFollowers and numFollowing isn't being updated properly. Going through the database I found users with multiple followers but not with the appropriate total number.