I have the same problem.
Example: On my 36" TV in the LR, all the cable channels come through. However, in the BR, Channel 3 is NBC Olympics coverage and I have picture but no sound. In the past I have had other cable channels that have not been present on the BR tv, but are on the LR tv. So it is not always a function of just doing a channel scan.
My theory: (remember it is theory) The park passes the signal down through a distribution panel (unit) and there are factors involved that include the switching, cables, connections, tv's, and signal strength performance caused by any or a combination of any of those items.
My LR tv is basically new. I installed it myself, whereas the BR tv is OEM. The sensitivity levels fro receiving signals "could" be different in that the LR new tv more readily accepts weaker signals.
So to the OP, try this. Come from the post through a window, temporarily, and bypass all the RV switching and cabling. If the channels are all there after you perform another scan then the problems is between the RV cable connection and/or switches. Check all the cabling and ensure that all the connectors are tight. Check the switch box to see if it is operating correctly.
What I would do at the switch box is disconnect the two cables, one from the outside bay and the other the output to the BR tv. put an inline connector in the two cables and try the BR tv again. If the channels are all there then the cable from the outside RV to the switch box is good. If the channels are not there the problem is in the switch box.
Others may have some ideas.
Wayne MSGT USMC (Ret)
2008 Winnebago Destination 39W
It is what it is, and then it is what you make of it.