It's probably a compromised coax cable drop from the pole or a line , hardware issue somewhere in the neighborhood. You need a tech out to investigate / correct the problem.
Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.
Good luck !
I had this exact problem. My neighbors and I complained for a while. It ended up being a coax connection on the pole at the top of our street not being completely secure and old. Tech climbed up tested both sides and reconnected with new connections and taped it. No problems for over 15 years since.