I've had this issue too. My computer kept trying to upload all my shit to One Drive which killed all speeds. I fixed that and things were fine for a bit but quickly started to downgrade. I've had some techs willing to do diagnostic shit. One even stayed on the line with me while I turned off and back on every device until we found the one that was the culprit. But that's another gripe I have with them: some techs are amazing, others just say "Huh, that sucks. Anyway, we're sending a tech out, but we can't tell you when and if they show up while you're not home, that's on you."

It's gotten to the point where I actively tell the person on the phone that I know a call ticket isn't going to fix anything, but I'm hoping to waste everyone's time and resources enough for CC to actually do something useful.