My bedroom cable has a splitter in the line that also feeds the outside jack (factory setup). Might research a problem there. My splitter is located by the video selector box, near the main TV.
Over the air signals have to be pretty strong for me to have the same channels playing on both TVs, cable no problem. For a weak signal, the bedroom TV goes south first.
Also had a problem once getting over the air stations on the bedroom TV after going to a campground with cable. I had to go into the TV setup and make a change there. I would run a cable directly to the TV and see if it works that way.