Don't know about Win a Bagel.
But ours as most or a ll run the slides of the house batteries we only have four 6 volts, some have as many as eight and newer ones have 12vots, or some of them.
We have one huge 12 v chasis battery that probably weighs 200 lbs.
We have a switch next to driver to bring the 6vs to bear if the bigun won't start the MH.
If you are exhausting your house batteries, start the generator to bring them up.
Charging from the converter side takes a lot longer and won't do 100%, I believe.
When we put new house batteries in even the generator took many miles down the road to bring them to full charge.
I cannot imagine why they switched your slide to the chassis battery, unless there is an electrical problem and it should have been fixed in the first place.
Do you have bad battteries?