More than likely, leakage in the coaxial cable, or a bad connector.
On my way home from work, there is a utility pole I drive past. Every time I would pass it, my VHF radio would go nuts on our primary channel. Same pole, same location, same frequency. It's a leaky cable TV coax connection. Sloppy install or damaged at some point.
A knowledgeable installer will understand why quality components and proper installation are necessary. Occasionally someone will try and "fix" it themselves. They'll often use cheap/low grade parts, improperly installed connectors, etc. and cause all kinds of issues.
Case in point: I work at a large research university. We have our own internal cable TV system. One of the students wanted to move his TV and used some #14 stranded wire he found to do it. He stuffed one end of the wire into the F connector at the wall, and the other end into the TV. Worked well enough in his mind, he got the channels he wanted.
Huge issue was that he created an antenna that was leaking the cable TV coax signal. While normally a very localized problem, we have an approach path for a very major international airport right over top of us. Aircraft coming in from Asia make a turn over the top of us on their initial approach. One of the cable TV channels matched up with the air traffic control frequencies. Every time the aircraft reached that turn point, they'd get a blast of interference and wouldn't be able to talk to the controllers.
This was one of those issues where the FCC/FAA did immediately get involved and showed up at our door. Radio direction finding was used, as well as shutting off different segments of the cable TV system to find the culprit. All done by a well meaning person trying to "fix it" themselves.
