Just got back from our trip to the Black Hills. The first day/night we had driving rains and thunderstorms. I later spotted a stain - looked like milk at first - on the floor in front of the heater. I thought maybe some milk had leaked out of the fridge, although I never saw any spilled milk inside the fridge. Now that you mention your experience, I'm wondering if we had the same thing. I'll be doing some more checking.
FWIW, the Black Hills were incredible. We camped at Stockade Lake North in Custer State Park, which had big, isolated campsites well away from the road. And the town of Custer is 4 miles away if you need anything - Custer State is a huge park, and you can be well away from any towns. Highly recommended. Saw Mammoth Wooly sinkhole and fossils, Mt Rushmore, and Crazy Horse. Highlight of trip was sunrise wildlife tour - herd of buffalo along the road, single buffalo playing, bull elk bugling and watching over his 30 elk herd (two different herds), deer, prong horn antelope, prairie dogs. "Where Buffalo roam, and the deer and the antelope play, and the skies are not cloudy all day."
2014 Rockwood A122 A-frame
2008 Hyundai Entourage minivan