Check the cable fittings. We had problems with our previous cruiser. Three cable connectors had been improperly assembled and the strands from the shield were touching the center conductor. Also check that all cable connections are tightly connected.
Dale & Carol
2010 CF30SK Patriot
I had the same problem and for several outings, I had to run the cable from the outside box through the slide seal to the TV. Warranty covered the repair, but I don't know where or what the problem was. I assumed it was a 'connection gone bad' somewhere.