Anyone else randomly dropping internet for 10-15min?

Just had a 15min outage on DHCP with multiple error messages "post auth result was not successful, session removed" on the Quic protal. Then it started working again. Nothing has changed at our end and the system has been happily running on DHCP since the functionality was publicly enabled over was made (openWRT on a nanopi).

I see there are a handful of similar messages over the last month and a half but only occurring once each time and not being noticeable rather than 15mins without a connection and 6 errors one after another. Based in the Waikato if that makes any difference.