Before assuming coax is bad, I would have to do some real tests as it is so easy to miss things like not having the settings right or looking at the wrong spot.
With a meter testing coax is actually quite simple if we know how to check resistance.
Think of the coax as two wires, one inner and one being the mesh on the outside, then do a check to see they are both open at the ends and check for any contact from inner to outer. Assuming none, then check that the wire you ID is actually the same as you think on the far end by looking for ground on one end while somebody putting the ground on one wire at a time at the far end.
If you see no short from wire to wire and do see the ground when applied to both wires, the coax is good.
However if you do not see it when the far end is grounded, I would first assume I have not found the right ends to match!
The last thing I assume is there is a wiring error or real problem as it is just so easy to not look and get it right when things are new.
But some info on components of the system location:
First picture is general area to find them, second is closeup for id of what may be behind panels, etc. hard to spot?
1. Power supply switch
2. dual coax
3.HDMI splitter
Info?
Have you found these for drawings of how it is tied together depending on options on your RV?
https://www.winnebagoind.com/diagram/2019/000164480.pdf
https://www.winnebagoind.com/diagram/2019/000177027.pdf
Linear Mode
