Very common to have odors from roof vents being drawn into the coach particularly if you have two open----warm air exhausting during a shower can create enough air movement to draw cool air in from the roof. I have those venturi things on my vents and it stipped that source for odors. Also in hot weather if you have a washer dryer the pee trap can dry out---just run the washer and it will fill again.
I do all my own stunts
03 Dolphin LX 6355, Workhorse W22, 8.1 vortec, 04 CR-V, Blue Ox, Brake Pro----Norm, Barb and
Doc(He's a PhD)