We're investigating a problem causing intermittent SIP call failures.
The problem is only affecting one of our call routers, which has been taken out of service. This means calls should return to normal while we're investigating.
Everything should be back to normal now, but some phones will need to re-register. This will happen in time, but if something's not working please re-register or reboot your phone.
Closing this status, as all seems to be well, but we're continuing our investigation into the cause.