12V circuit only works on shore power or generator

Would check the relay that does the transfer for the 12V, as with our rv i have 1 circuit that is a direct battery connection for the radio ( separate fuse) , the rest go through the transfer relay, ours also has a battery disconnect switch which will kill all 12Vs from the battery to the 12v panel as well too but still work fine off the generator or shore power but will not charge the RV batter when off.

The RV battery is only 2 years old and I take good care of trickle charging. I took a meter to the panel to check the voltages. On battery power, the main wires to the 12v panel were 13.45 and the same was found at each fuse

What surprised me was that when I measured with shore power the voltages dropped to 12.8. I thought since the problem was happening on battery power, that the voltage would be lower on battery not higher.

battery