Marking a notification as read is not always taken into account right away

STEPS TO REPRODUCE

1. Login as Admin
2. Set all Notifications to ON
3. Watch the wiki
4. Login as another user (e.g. U1)
5. Create/update/comment/delete a page
6. Login as Admin
7. Go to Notifications > Settings and Set 'Read Event Filter' to ON
8. Mark 2 event as read
9. Refresh the page

EXPECTED RESULTS

The read marked events are not displayed on the list anymore, the count shows 2.

ACTUAL RESULTS

Even if 'Read Event Filter' is set to ON, the list displays all 4 events (2 read and 2 unread) and the count shows 4.

If at this point the 'Read Event Filter' is switched to OFF and the page is refreshed, all 4 events are displayed in the list (the two read events are displayed now as unread), although the count shows 2.

Furthermore, if 'Read Event Filter' is switched ON once again and the page is refreshed, the list is displaying (as it should) only the originally unread events, with the right count (2).

The issue could not be reproduced on XWiki 10.11.3 and 11.1.