The scenario:
Headed out Friday midday for the local COE park. Weather was forecast to be pretty sporty Friday night. The drive/tow up was without rain and uneventful. Unhitched, leveled, attached 50 amp, pressure regulator, water filter and FW (yes the nautilus was set to city water). This was the first trip since de-winterizing. We are noticing a fair amount of air bubbles in the water. Pass through doors were closed and locked before storm came in.

Friday beginning about 2200 and lasting until 0200 or so we get sideways rain for about 4 hours and 40 to 50 mph winds. The remainder of the weekend goes very uneventful, trout fishing, camp fires, no water issues with the exception we are noticing what seems to be an unordinary amount of air bubbles in the water coming from the faucets and toilet flush. No water pressure issues.

When we are packing up, wife notices a large puddle (maybe a gallon or two +/-) in the pass through. My immediate thought was an issue behind the nautilus panel as nothing inside the pass through from above. I take everything out, wipe it up with several towels and then remove the basement walls on both street and passenger side and everything behind the wall is dry. I meant absolutely bone dry. I have DW run all faucets and no visible leaks. I switch to the FW tank and run the pump, no leaks. I am unable to replicate any water intrusion.

I open up the front compartment and everything is dry. Up on the roof, all sealant looks good. No evidence of water intrusion inside. I am absolutely stumped.

I welcome any thoughts