Internet Drops Intermittently for ~30 seconds

I have had my xfinity wifi service for over a year now, 200MBPs in a 1 bedroom apartment with my fiance. We have been experiencing the internet dropping the entire time, where every so often, we will lose the ability to stream netflix, stay in an online game of xbox, more recently lose connection to host in Zoom work meetings etc. We also have the xfinity app on our smart tv instead of cable box; and if we are watching tv we frequently get interruptions.... Very frustrating. We have called xfinity a couple times, they have done their resets, turned it off and on a bunch of times. Still happening. Today, they came to the apartment and changed our coaxial cable that ran from our unit to the modem as it was old, and the problem persists. 

What direction do we go next? We live in Chicago, the speed is great when it works. 

Note, we use a Netgear c6300 router. when we lose the connection, the router never indicates the internet is off or rebooting atleast that I can tell...