We have a 2018 FR3 29DS and last fall, while camping, we started noticing a bad smell. After returning home, I climbed on the roof, removed the black tank vent cap, and ran a sewer snake down the vent till it stopped, and marked the snake at the top of the vent. Pulled it out and realized the length from the end of the snake to the mark was not enough to reach the bottom of the tank. I reinserted the snake and started working it up and down till I felt something break loose and the snake went down a considerable amount more. Evidently, something had blocked the vent, and I had broken it loose. Not sure what it was but this eliminated the smell and haven't had problem since.
The way I see it, you can either work for a living or you can fly airplanes. Me, I'd rather fly. Len Morgan
2018 FR3 29DS
TOAD - 2002 Toyota Tacoma 4WD