Activity Stream does not load/display events properly anymore

STEPS TO REPRODUCE

1. Login as Admin (or an user)
2. Create, edit, comment some pages (more than 10 actions)
3. Go to Dashboard
4. On Activity Stream, click 'Load older notifications'
5. Logout (and refresh the page if needed)
6. Click 'Load older notifications'

EXPECTED RESULTS

The notification events are loaded properly when clicked 'Load older notifications' for a logged in user, as well as for guest user.

ACTUAL RESULTS

An endless spinner is displayed instead for a logged in user, events are not loaded.

For the guest user, after 'Load older notifications' is clicked, the events are loaded, but they are marked as they are already read (white background); however, they are loaded separately from the list, sometimes on the top (along with RSS feed link), sometimes on the bottom.

The same behavior has the Activity Stream from the user's Profile.

The issue could not be reproduced on XWiki 12.1 and XWiki 11.10.4.