@Virgo Thanks for the reply. None of these suggestions worked.

1. Ensure the OC200 can get Internet access

Confirmed . no issue with internet connectivty. Controller can reach outside services.

2. Ensure the NTP Server is configured properly.

When changing the timezone, the time/date is refreshed correctly. Therefore the NTP server is correct and working.

3. Ensure the DNS server can resolve the NTP Server successfully.

DNS in use is 1.1.1.1 and devices within the network can resolve no issue.

4. Ensure the OC200 keeps running for more than 24 hours

Issue persits through multipe days with no resolution until the timezone is manually changed.

5. Turn off Modem/Router Firewall settings or lower firewall level for test purposes.

I use the ER605 so unsure how to change these settings in the Omada software, but given other devices can use the same servers to sync time, then it doesn't seem a likely step.

However, I changed the domain of the NTP server to an IP address, and so far the issue has gone away. However, somehow the controller occasionally fails to resolve the domain and gets stuck despite that the adress can be resolved with no issue from other devices in the network.

This IP address 'bandage' seems to work for now.