When using the antenna you need to have the antenna amplifier 12v power supply ON, and when using cable or satellite it should be OFF.
The button to turn it on or off is usually in the cabinet over the co-pilot seat (near the front TV. When it's ON there is a small green LED indicator. This one switch affects the signal for both front and rear TV (if equipped).
You probably have it ON,,, and that would interfere with cable & sat signals and make it seem like it's broken. Hope this solves your situation!
Larry