Is this a class A or C? Do you have a solid state battery isolator? When you were replacing cables is it possible that you loosened a cable connector to something? You probably have a transfer switch if you have a built-in generator. Do all of your 120V devices operate on either shore power or generator?
The strange thing is that if you have 11.4 V at the battery terminals (dead battery, BTW), you should have that same voltage throughout your 12V system. It should not go down to 6V unless you have a shorted cell.
