A related issue...

Though it's not the source of your problem, you might want to look into the
possibility of ground loops, especially if you wind up making an analog
connection between the Panasonic and your system.

It's difficult to find RF isolation transformers for cable systems. MCM
sells one -- the #33-8700 that seems to work okay. It's sometimes available
for ~ $10. You might also want or need a double-F connector, #33-480.