You are probably not at a CG now but on your next trip, if you have a long enough cable, try hooking the park cable directly to your rear TV. If the picture is better, then you have a loose connection between the splitter and your rear TV. If the picture is not better, then the TV's tuner is most likely the issue.
In my 2014 FR3 30DS, the cable is high quality 3GHZ rated RG6 with high quality connectors. However, when I installed my Dish receiver, I found the most of the connections at the splitter were loose. I was able to remove the wallplate (with the antenna booster) and pull the splitter through the hole. If you can't do that, you can reach the splitter by removing the head unit.
Lastly check the coax connectors behind the TV. I don't recall if there is a wallplate back there or not. I also don't recall how to remove the rear TV from the mount, but I don't think it is difficult.