I've spoken to Orcon support (confirmed the symptoms, promised to call back "in an hour when our support system is back online"). No follow up from phone support team.
I've filed issues via Orcon's online "support" system (5th September, ticket #11905688). Their response in the support queue to date has been pretty much "plz reboot router".
Hey Orcon! Help us out here. We pay your bills, can you please make our phone work like it ought?