First older notification event loaded in Notification Menu is duplicated

STEPS TO REPRODUCE

1. Login as Admin
2. Create a global user (e.g. U1)
3. Login as the user U1
4. Go to Notifications > Settings
5. Set all Pages Notifications to ON (watch entire wiki)
6. Login as Admin
7. Create, update and comment some pages (e.g. 11 events)
8. Login as the user U1
9. Open Notifications list and click 'Load older notifications'
10. Observe and count the events
11. Go to Dashboard's Activity Stream
12. Click 'Load older notifications' and observe the events

EXPECTED RESULTS

After clicking 'Load older notifications', only one more event is loaded, as they are 11 in total.

ACTUAL RESULTS

The 10th event is duplicated in the notifications list, so in fact 2 events are loaded.
The same happens on Dashboard's Activity Stream after clicking 'Load older notifications'.

The issue reproduces also on XWiki 12.5.1. I've tested also on XWiki 12.1 and I couldn't reproduce the issue.