Error on Netgear device: Started Unicast Maintenance Ranging - No Response received - T3 time-out

I am receiving these 5 errors on my Netgear C6220:

• 16 consecutive T3 timeouts while trying to range on upstream channel 1
• Unicast Maintenance Ranging attempted - No response - Retries exhausted
• Started Unicast Maintenance Ranging - No Response received - T3 time-out
• Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out
• MDD message timeout

These are causing my router/modem to lose connection to the internet & requires that I power-cycle the router.  Happens every 2 hours or so. Is this an issue with the service or with my router? Thanks for your help!

**EDIT** A tech visit failed to solve the issue & the corporate employees refuse to answer my messages now. I am losing connection at least 10x/day, making the service basically unusable. All be warned who are having similar issues! I will be switching to the city broadband the second it's available in my neighborhood.