Meanwhile, I had a job to do which no one would really enjoy doing. The seal on the knife valve for the black tank was leaking. The leak was no more than a slow drip but it would collect in the clear section only to spill when I removed the cap.....yuck!!!! So I had to empty the tank and flush clean.
After removing the valve assembly, I did find some material buildup in the slot where the knife seal runs.
I cleaned, lubed, and reassembled the valve and kept my fingers crossed. So far it seems to be fixed, I'll see tomorrow. Now to get the smell out of my nostrils.