1. I assume you still have the 2003 HR?
2. If so, there are 2 ways to sense temp on your 5 button Dometic CCC system----1. The Main tstat IS the sensor for Zone 1 and you have the remote sensor in the bedroom area for Zone 2---2. They elect to NOT use the tstat as the Zone 1 sensor and use a standard Temp Thermister like the one in the bedroom. They usually do this when they mount the wall tstat in an area that is not good for sensing the interior Zone 1 temp
3. IF you disconnect the Zone 1 wall Temp thermister, that makes the WALL tstat the temp sensor whereever it is located.
4. The Zone 2 is indeed run thru the Zone 1 control board in that the communication goes thru the Zone 1 board, but the Zone 1 board does not control any aspect of the Zone 2 AC unit.
5. Do you have the low profile Penguin series model AC units? If so, the odds are from the age of the RV that the communication phone type canles at the AC units are corroded from humidity during the past 10 years. Very common on older Penguin model AC units. You need to check and verify all of the phone wire type connections at the AC units. Doug