Northstar campers

I had a Northstar 850 with a cassette. Now I have a Lance 820 with a black tank. This week I developed a horrible odor from the toilet. It appears that particulate matter doesn't always flush out. Pieces stick to the sides of the tank, dry out, stink up the place. I spent a good half hour filling, spraying, bleaching, emptying, etc to get it back under control. My cassette toilet never did this. Empty, rinse, repeat. Anyplace. Winter time just fill the reservoir with windshield washer fluid. If you are in a CG with septic, sure, it's easier to hook up and pull the lever a few times but in the long run the cassette is far easier and less work.