Mine has done this too, but also make sure of what you are smelling. Pour water down the sink to put water in the trap and lots of times the smell goes away as you are smelling the grey water, not the black water with chemicals. Every once in a while it is the black water tank. I just add a little more chemical and it's done. But when that failed, is when I found the smell coming from the sink.
2012 Sandpiper 365SAQ weighing @ 15k, Onan, 2nd air, slide toppers, TST
2013 F350 6.7L Lariat 4x4 CC DRW,Viair 1007, Ride-Rites, Edge CTS, B&W
2001 Chevy 3500CC DRW 4x4, 8.1L, 4.10 gears w/ Detroit TrueTrac
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