IF they are more than three coaxial lines, it is possible and somewhat likely that there is also a drop-amplifier in use. Typically, after an ordinary cable signal is split 3 times + the picture quality begins to suffer. Some people use drop amplifiers - like a coaxial splitter, only powered. If there is one in place here, you may wish to find it and remove it as it may be plugged into a receptacle.
THe use of a drop amp here is questionable though, it doesn't sound like the home owner knew what they were doing in the first place. I guess it may be unlikely that they knew anything about drop amps. HOwever, its worth a glance.