I also have a 2003 Cheetah.
I have had electrical problems with my house battery bank draining.
I tossed the factory batteries and went to Glassmat batteries, which lasted four years before they were toast, and they were foamimg toast when I looked at them ( I was on assignment in another state for a year).
There is something integrated through the inverter that draws power with the main coach disconnect turned off; I have not traced it, but it will draw on my engine batteries.
Not an answer but another place to look for the root problem.