Dont know if it's the same but we had a smell. it occurred after we emptied the cassette. We would be driving along and go inside for morning tea etc and it was disgusting. The only thing we changed is to make sure there is no water in the bowl before emptying the cassette. It appears that I may have been hasty closing the trap door and toilet lid and maybe didn't let all the water go. When the cassette was emptied and the seal was broken the residual water leaked into the toilet cassette cavity. Is your cassette cavity wet? Not much of a solution for you but it has worked for us. Something so simple.
Lomes, have a talk to the local Bus/Coach company or a Coach Driver and ask them to show you or at least tell you how the Coach set up works. I am not sure of the workings but never had a smell problem when driving them. I only did day trips and the boss always emptied the tank at night to save paying overtime.
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Live Life On Your Terms
DOUGChief One Feather (Losing feathers with age)
TUG.......2014 Holden LT Colorado Twin Cab Ute with Canopy
DEN....... 2014 "Chief" Arrow CV (with some changes)