[Motor31]

Have you checked to see if the vent pipe has dropped down? It should be a double layer pipe on the roof. The vent pipe should be inside the extension that goes through the roof. If it has dropped down below the level of tank contents the tank will vent inside the trailer due to gas build up.

Have you also checked in the basement for leaks or tank problems? The black tank is the top most tank just under the commode. On my rig it also has the water pump mounted on it. Look for abrasions, scratches or a leaking valve. Fortunately that valve is easy to get to. Mine was already replaced with a standard non pull cable valve when the cable mechanism got too sticky to function. It's no big deal to me to slide the basement door open and pull the handle.

20 mule team borax will help remove the odor of spillage if sprinkled (dry) onto the spill.