No matter how clean the tank is it's going to be "dirt" the first time you take a poop or pee. If the tank is not being properly vented from the roof vent you're going to have stink and pressure building in the tank during the day and when you flush it that pressure and stink is going to be relieved into the RV.
Make sure the tube is not obstructed by the vent cover. There should be an inch or so of gap between the top of the tube and the cover. If there is an appropriate gap remove the covering and look down the tube with a flashlight to see if it is obstructed. If there is an obstruction you can pour water down the tube to try and knock loose the obstruction or tie something heavy to a string long enough to reach all the way down the tube to dislodge the obstruction.
The one time we had a problem with black tank odor it was caused by a too narrow space between the top of the vent tube and the tube cover (either the tube or tube cover shifted at some point during our travels). I removed the tube cover, checked for tube obstructions (none) cut 1/2" from the top of the tube, replaced the cover and the issue was resolved.
We have never clean our black tank but we always use a deodorizing packet after each tank dump putting a gallon or two of water back in the tank to prevent whatever is left over in the tank after we dump the tank from hardening. Six years and never an odor issue other than the one time the tank vent was obstructed. That said we did not have sensors in the tank and I understand that cleaning the tank via a black tank flush is something that helps keep the sensors operating properly.
