I work at an ISP and we have guys doing this constantly. It’s not always at a customers house but yeah. A fault on the cable going to your house causes your modem to increase the power it uses to talk to the node in your neighborhood that connects back to the ISP. If your modem uses too much power and drowns out the signals from your neighbors going to the same node, then everyone else’s service can suffer and yours is just fine. It’s weird but that’s how it is.

A connector might have gotten rusted or a landscaper might have nicked a cable with a weed Wacker or something.