Hi Oranged,
I didn't reboot the router myself, it automatically resynced.
Yes, that's a quirk of the O2 firmware I understand. That's why I suggested re-syncing at a more suitable time of day because those auto resyncs always seem to occur late in the day or when you're asleep
Even though you may not have received the "testing is over " message from O2, it does no harm re-syncing during this period (because there's no Big Brother of a DLM watching you).......but it's your choice
If you choose "Restart" from the O2 Wireless Box II menu on the config page, then I understand that shows up so that O2 technical team can see that it's not an "unusual occurrence".
This was proved to me recently when I phoned them re. a disconnection problem.