Since about December, when playing games on my home network I'll randomly disconnect from the server (anywhere from every 5 minutes to 3 hours). It happened with Star Wars Battlefront, Smite, and now CoD: Warzone (which is the biggest problem since I can't rejoin the game after disconnecting). I also use GeForce Now to stream games and, while it usually works great, occasionally it will get very blurry and I'll get a warning about having a bad connection. My internet connection consistently runs around 100 Mbps and very rarely slows (aside from the disconnects). I also don't experience any lag or other network issues before the games disconnect.
To test the problem, I ran NetUptimeMonitor (https://netuptimemonitor.com/) while playing CoD: Warzone and ran a web monitor (https://isp-monitor.appspot.com/#na) on another computer and neither of them showed a connection failure when Warzone disconnected from the server. Both computers are connected to the router via ethernet. I also called my ISP (Verizon Fios) over the weekend and they said they took some "precautionary measures to fix it", yet it's still happening. Because this happens with multiple games and GeForce Now, I can't shake the feeling that the problem is with my network and not the servers.
Also, I set up port forwarding for both Smite and CoD: Warzone, but it didn't seem to make a difference.
1) Is there a good way to definitively determine if the problem is definitely on my end or the server's?
2) If the problem is on my end, any idea as to what it is and how to fix it?