Not sure it has been mentioned but the electronic sensors in most RVs, even in my old '94 Bounder, sensed the condition of the house batteries AND the output of the alternator on the chassis batteries or battery.
IF there are any weak or defective batteries in this setup, the house batteries will not be charged as that could damage the alternator and cause the driver to be stranded on the highway. And that takes precedence over charging the house batteries.
So if the chassis battery is weak, and the alternator has to really work to move it's voltage up to an acceptable voltage, the house batteries won't be charged until a minimum charge value is reached, if ever. And IF there is a house battery with a bad cell, for example, and it's voltage doesn't come up to a minimum level, then again, the BCC won't allow the alternator to try and charge it.
At least that's the way the BCC in my old '94 diesel pusher worked.
So the question I'd have for the OP is, how old are your batteries? Have you had them load tested?
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