Intermittent internet outages

We've been having intermittent internet outages that last between 30 seconds & 5 minutes occurring between 5 and 30+ times a day for the past 6 weeks. I've tried the Xfinity assistant and had 2 or 3 chats with live agents & followed their instructions (mostly just restart the router) to no effect. I've also replaced both the coax cable inside the house as well as the barrel connector, which obviously didn't fix the problem.

The problem occurs on all different types of devices (smart tv, tablet, phone, smart speaker, etc) and on both wifi & Ethernet connected devices. I would also note that even when there is an outage, the lights on the router do not indicate a problem, which seems odd. Our router is the ARRIS xb3. At this point I'm thinking I need to either replace the router or get a tech to come out (assuming I can actually get a real person on the phone).

Any help would be appreciated.