your RV is old enough to have an old magtec converter for charging
and depending on the which model number converter
they had a 6 amp charging circuit and a 30amp power circuit and a reed leaf relay
that switched out the battery and the converter supplied the battery and house separately
that relay is inside the magtec, behind the fuse panel
I think it is failing and sticks (this is why it doesn't switch back to battery immediately) , and the 6 amp charge is way too low, for charging from generator, your batteries are possibly in bad shape from not getting charged and then being dragged down again
it will take about a week on shore power to completely charge the batteries using the magtec
you need a new high rate smart 3 stage converter OR an external high rate battery charger
