I strongly suggest that you take the interior trim panel that covers this wall off for a look-see.
just above the area where these photos were taken.
In mine it is an upholstered cushion with buttons. The buttons are simple old fashioned snaps like you'd find on clothing. Under them are screws. very easy....
I discovered a similar think on mine, turned out I had a leak up top that was running down into this little wall. Safe bet that it had been leaking since it left the factory....just a tiny minuscule leak over time....
I sincerely hope you find that yours is only from road spray from below....
the good thing, you are still under warranty. I was not when I discovered mine.
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