The wire is probably your easiest troubleshooting test.
Hope that's all you need for the pesky nuisance.

I have a really bad one from my cable provider even get frequent drop outs cable and internet. So far about 4 tries and the last round a guy admitted they need to put a new connection to my building.

luckily I have an older Monster Power center with a Ground loop isolator built in works magic for the time being.