We just purchased a used TT (made in 2020) and when it was delivered, the bathroom didn't smell. After 2-3 uses though, the bathroom started to reek of pee! We have cleaned the bathroom top to bottom daily and it seems to help for a short time, but it always comes back! The smell never fully goes away. We have emptied and flushed out the black tank, washed the walls, the floors and, of course, the toilet. We have owned RVs before that were older and have never had this issue. It is bad enough that the bedroom get filled with the smell as well. Any ideas?