My understanding about the electrical system. When you are plugged into shore-line the Convertor takes over and supplies a balanced 12 volts to the RV. Yes, the Slide motors are 12 volts. House batteries are only used if you are dry camping I believe?
When I first drove my new RV to my shop I plugged into 30 amps. Every component had power both 12 volts and 120 volts. A few days later I found out my house battery switch was OFF. Interesting in the OFF position my RV was getting all it's 12 volt power from the Converter. But the House Battery Switch needs to be on for your batteries to charge!
BTW...I downsized from a 40 foot Diesel Class "A" and the inverter had to be operating to get 120 volts. The four house batteries were used all the time to power 12 volts to the coach. So, the inverter/charger was constantly charging my house batteries.
Sounds like your Battery Control System still has a problem.
2013 Forester #3051SF
2009 Toyoda Tacoma (toad)
2010 Newmar Dutchstar (Sold)
2011 Fleetwood Bounder (Sold)