Do not let moisture remain under the door mat. I have a new black mark on the floor from this same problem, and it happened fast. I'd post a picture but photos are not working on this site currently
If it's not I use at the time and the fridge is not running tape some plastic inside the vent door, remove before use.
Is there screen on the inside of the vent doors? If not rivet some aluminum window screen to the inside, ant water that gets past the louvers should hit the screen and run down and then out. Small gap in the gasket bottom behind the hinge should allow a drain path with hinge blocking inlet of water. Look at it, I'm not sure how newer doors are set up.
Sorry I did not. I was told it was from a “black coating?” Which Airstream puts on before the floor. So my black stain was from a rubber mat being wet on the bottom from a leak, and the stain welled up from under the floor. That was over 3 years ago, and I no longer have that trailer. Good luck!!
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