I enable SPI Firewall and now also have good uptime. 2 days and counting.... EDIT...AFTER 2 days same behaviour.

Gaara wrote Can reboot makes the router work well again, or the issue still exit after rebooting? After rebooting, everything works for approximately one hour and then the problem returns.

To be clear, this is not a VOIP problem per se. The entire modem is unresponsive, no management, no Internet, no VOIP.

Yes, I hae the latest firmware and have problems.

I contacted them and they got me to reboot and check I had latest firmware. Not able to help at all. They did say they are working on new firmware version but had no timelines. Said to watch this...

Really? Where is the new firmware. Any timelines?