Haven't heard of any MH with dual output, diode controled, converters. That sounds more like a boat thing.
If your Class C has the capability to charge the chassis battery, while on shore power, it would most likely be thru a BIRD ( Bi-directional Isolation Relay with Delay ).
A BIRD is a voltage sensing device that confirms your house battery bank being charged to a specific level, before connecting the chassis battery. Sort of like an automatic boost switch.
I would confirm with the manufacture that your MH has the capability of maintaining the chassis battery on shore power, before digging into the system. Not all do.
Since you say this is a recent problem, you could have something drawing down the battery on the chassis, unrelated to the house systems.