Internet Connection is unstable despite Xfinity support trouble shooting

Internet connection is unstable. The xfinity app and sites run their tests and say it all works but I can't be in an online call, or stream a show, or what have you without repeated internet drops. Sometimes the connection is wholly unusable and I have to write off using wifi for the day. All while xfinity app says my connection is Perfect! Resetting gateway, unplugging router, restarting devices, nothing changes the problem. This is both on my desktop, with an ethernet connection, and in wireless devices. I have tried adding extra fans thinking it might be overheating, changing the channels to avoid overlap with neighbors, and splitting my bands to see if it's a swap over between bands and none of it works for wireless my limited wired connections are the same.