Kind of scared to ask questions or to respond, but you asked if we had the leak and how did we diagnose.
I had the water leaking in my lower compartment driver side. I first noticed at a gas station while waiting on the gas tank to fill.
1. I ruled out rain as no rain present for several days.
2. I checked for smell, freshwater, gray or black? Ruled out black as water was clear, but I could NOT tell if it was Fresh or Gray.
3. Checked my tank levels (I did for real) Gray was Full, Fresh was showing 1/3rd tank
4. I decided to continue the trip home (I was bout 3 hours away)
5. Drained the Gray tank & cleaned it all out with wet vac and left all compartment doors open for it do get air overnight and the next day it was bone dry.
6. You may not like this one,
but I did exactly what that Damn Duck guy told you to do which was to "Drive it a while with the (Gray)
tanks not overflowing (Empty)
?" Of course it remained dry; so I knew my gray tank was leaking at some point after the 2/3rd mark.
7. I took it back to the Dealer as my coach was under warranty as it sounds like yours should be. I told them specifically what I experienced and diagnosed, within an hour they call me back and said a fitting above the tank had sprung loose, the water sloshing around while driving with a close to Full or Full tank was the issue. They fixed it under warranty and I picked my coach up 2 days later.
In my case it did not leak on both sides nor did it go into more than one lower bay compartment, but it could have easily based on the design of another coach.
I was very glad I had the issue when I did to have it fixed with warranty. Oddly we knew the Gray tank was full, but we ASSUMED the bathroom sink was draining to the black tank, we kept using bath sink for about 2 days when gray was full. Our SOB coach is plumbed so the bathroom sink goes to the gray tank
Since then I have mastered how to access all of my coaches wiring & plumbing diagrams to assist with diagnosis such as this.