That is exactly what the problem is. The wax rings with the plastic horns are a worthless piece of junk that should be banned from the face of the earth. Even if they don't cause a problem such as you are having, they perform no useful purpose. Some marketing genius figured out they could make a little more money for DIY suckers who would think that that funnel would somehow be better than just the Plain Jane Wax Ring and they could sell it for more money. These are a bigger problem in 3" drains than 4", but they are just crap!