TV cabling inside trailers is done by aliens, late at night. Where they go is a mystery to all owners.
Often you have to tone out each run to see if continuity exists. Sometimes the cabling is different colors and you can pull out the connector plates to look behind and see if same color comes out where it should. I did that and figured mine out....mostly.
But it does sound like a continuity problem. Loose connections maybe. Wrong connections maybe. It's a PITA, but you have to run it all down. My last camper, I just ran a flat coax through the window, also.........and of course that worked when nothing else would.
"Next to prayer, fishing is the most personal relationship of man" Herbert Hoover
"American by Birth, Southern by the Grace of God"Lewis Grizzard
2016 GMC Denali 3500Dually--2017 CC 36CKTS