Busted,
I had the same problem with water leaking underneath the fire extinguisher into our kitchen while sani flushing my black tank this summer. It happened two days in a row, then ceased and desisted. We pulled the extinguisher off and besides water, dust, and wood shavings besides whatever they left behind and could only guess that the hose connections might have leaked under pressure. I was told by one of the Heartland warranty reps that it could have been too much PSI at the campgrounds. In the next sentence, he told me I don't need a water pressure gauge at the water source, as our hoses can take lots of pressure. Luckily I read the Heartland manual which said do not exceed 65 lbs PSI or your warranty will be voided. He stood corrected and said follow the manual.
So far, it hasn't happened again and the repair shop could not duplicate the problem. Good luck it sounds like you got some good answers. Check out your hose connections for sure.