1. You did NOT say you had it set up to toggle between the 2 sats. THAT will make it do what it does
2. The Voltage IS critical. WHAT is the voltage and don't say 12+. Give the actual voltage. Domes, not just KD, are required to have a 12.6 voltage and above to function correctly. That is why some Dome makers want you to use a 120 volt to 12 volt transformer to make sure you have the required voltage at all times
3. That extra cable will not affect your voltage supply as along as you have a GOOD supply. The fact that you state with the 12 volt charging system on (APU or Shore) and the KD operates correctly, then your battery 12 volt supply is not correct. A GOOD 12 volt supply will have at a minimum 12.6 volts. Doug