With two alternators the house and chassis batteries are charged independently.
I would rather see the voltage at the house battery posts, although it sounds like the house generator voltage regulator is in bulk charge, or there is a problem with it. I would not allow this condition to continue.
You did not say what the house voltage is with the inverters (on shore or generator power) only charging the house batteries, nor did you say how long after engine start the voltage reading was taken, nor the battery voltage prior to engine start.
When Liberty looks at the added wires, they should also check out the house battery voltage issue and I would be inclined to take the belt off that alternator while driving there.