ISSUE SUMMARY:
If you add a user to some new groups in the backend 'Members' area using 'Assign to Group' an email and notification is sent to admins of the groups they are already in. This causes confusion.

STEPS TO REPLICATE:
1 user X is in groups A, B, C
2 Site admin adds them to Group D in the back end in Members using 'Assign to Group'
3 Group Admin of groups A, B,C get a notification that user X joined their group
4 they are confused as they thought this person was in their group anyway
5
RESULT notification is going out to pre-existing groups when you use 'Assign to Group'
EXPECTED RESULT notification should only go to the admin of the new group that the user joined, and not to all groups . e.g. Group D, but not A,B,C
BROWSER

Hi, Susan.

Thank you for reporting this. It seems like JS "thinks" that users was also newly assigned to groups he/she is already in. I was able to replicate this issue so I'll report it to our developers.

Hi, Susan.

Please, make safe copy of this file;

ROOT/administrator/components/com_community/controllers/groups.php

Then replace original with patched file from package.

This fix is for JomSocial 4.1.2 but I remember that you didn't upgraded to latest version yet.. so you'll need to use diff checker... or send this printscreen to your developer so he could just apply those changes:

i.imgur.com/WboJdKC.png