What Donn says is exactly right. For some unknown reason the cable connectors and splitters used in the RV's are of the cheapest quality they can find and the connectors look like a butcher hacked them on. I had the same problem as you and have told this several times here. I replaced all the connectors with quality cable connectors I obtained from the cable guy. I also replaced all the splitters with quality splitters again from the "cable guy". After doing that my satellite is perfect on all four tv's in my RV.
Also if you have a tv amp usually near the main tv maybe in the wall. It will look like a cigarette lighter plug. It will have a LED light with it and a small black button. Make sure the light is off for the satellite to work in the rest of the RV.
If you change out all the crappy crimp connectors with good compression fittings, change out the chinese crappy splitters and you will be good to go.
Oh, the hardest part is finding a helpful cable guy unless you but a compression tool and compression fittings.