Batteries lose power after coming home???

We take our R-pod RP-180 on a 2 - 4 day camping trip. Boondoggle. Don't use the lights, or radio, or water heater or water pump too much. Seem to have plenty of electric to get us thru. 

We drive 2 - 4 hours home (which should be charging the batteries). We get home and the batteries read just about what they did when we hooked up to leave our campsite. (ie 12.04 the last trip when I actually took a reading as we broke camp)

We arrive home and the batteries read 12.04. I disconnect from the tow vehicle and plug into shore power. 

Two days later we notice the LED lights are quite dim in the camper when you turn them on. Nothing is running in the camper. No fridge, lights, radio, furnace... nothing. I take a voltage reading 8.40 volts!!  

An no, the electric brake emergency cable has NOT been pulled. -- that happened once as we arrived at a campsite, so I know to look for that. 

So what is drawing down the batteries even though we are plugged in??? 

Only thing I can guess is that I BACK into our site at home, and the truck emergecy brake engages. I unplug from the vehicle and that the Rpod electric brake is somehow remaining engaged???? Seems far-fetched.

Any ideas?

Ken