I did an aggressive flush yesterday while I was washing the trailer, 10 gallons down the throne using a 5 gallon bucket, and as fast as I could get it to go without overflowing the bowl trying to wash anything out in the line since it appears the toilet has some pipe between it and the entry to the tank. Regardless if something was lingering in there it should vent out. Shortly I will be swapping out the gasket, I'll report back.
Based on the fact our black tank fills pretty fast, I'm pretty certain our bathroom sink also dumps into the black tank, and I'm suspect of a one way check valve abs vent tucked between the sink trap and the depths of the void behind the roll out microwave and pantry cabinet. Worse yet, it appears to not be a thread in style, rather glued in, and it's tightly wrapped with a bunch of 12 volt
wiring for the water heater I believe.
Before I get into that I'll try the toilet work first. Yes the smell is there when we camp, especially if using the fantastic fan or any of the exhaust fans, but builds in storage.
I'll look under the closet too.
As for the AC unit, I think it's more that the cups are now the point of contact instead of the actual mounting flange on the roof opening. I'll post pictures here shortly showing the difference. They did the modification to both units.
Thanks for the tips!