Internet cuts in and out all the time

I have had Xfinity internet for a little over 2 years now. I use the 1000mb plan currently with a Netgear CM1200 docsis 3.1 modem and a TP-LINK Archer AX11000 router. The first 6 months or so the internet was fine. All of a sudden after that we started having issues with the internet dropping out constantly. At the time I believe I had the 600mb plan, so I upgraded to the 1000mb thinking that maybe we just had too many devices connected and our internet speed wasn’t high enough. From here we begin to have even more connection issues cutting in and out multiple times a day. Sometimes it’s out for a few minutes and sometimes it’s out for as much as a half hour. Restarting the router and modem occasionally fixes the problem but only for the moment. 

They finally sent techs out multiple times and all tried different things. Speeds and connectivity would improve, but after a few days we would be back to constant drops again. Finally they replaced literally every single cable from the coax all the way to the pole in our backyard so that literally every single thing was brand new. And we are still having the same issues. 

I’m tired of speaking with someone who barely speaks English and them telling me “have you tried restating your router and modem.” The techs can’t figure out the issue. Is there any suggestions out there or something I could try? I’ve also replaced the router once to see if that could’ve been the issue. I’m considering a new modem just in case I somehow got a dud? But I hate dumping more money into a problem that may just be from an internet company that isn’t that great. Any help would be greatly appreciated!