In my camper, using either the Antenna or connected to rv park cable, the tv in the front of the camper and the one in the rear of the camper work just fine. Actually there is another cable jack by the front bed I've never used.
I don't know if that makes any difference if the camper was factory wired for 3 tv's or not but at least two of them work fine ... never hooked a tv to the 3rd location.