@jrsy 

Look at the internet LED light to see if it is going amber or stays green. If it goes amber, then it is no longer getting an internet connection from the modem. I would look at the modem and see why is it no longer supplying an internet connection such as contacting the ISP and mentioning that. 

What you can first try is to replace the Ethernet cable going from the router to the modem.

If you have a cable modem, you can log into the modem itself and look for any critical 3 or critical 4 errors in the system logs. Those pertain to signal issues that are over the cable line, and not in the modem. 

If the issue is happening as soon as an hour, you can try connecting a computer directly to the modem and leaving it for several hours to see if the same issue happens.

If the issue seems to stay with the router, I would reach out to our support team as the WAN port may be suspect: link

I ended up disabling the guest wireless networks and disabling OFDMA. Problem seemed to go away. I just enabled the guest networks to see if it shows up again or not. I think OFDMA might be the culprit.