I don't think the outside vents allow anything inside the heater box. Furnace vents are on the floor correct? One or more of them flooded somehow from the inside of the trailer? That could be a real problem down the road if subfloor was soaked.
Take it back to the dealer quick!
Charles & Martha Myatt
2009 Duramax w/Transfer Flow Fuel Tank
2016 Flagstaff V-Lite 30WFKSS
Almost South of the Border