I have a fairly new American Standard VorMax. Lately about one in ten times it will not flush liquids. I hold the handle down until the tank empties, but it still does not clean the liquid from the bowl. I used a closet snake on it, had the drain pipe checked with a camera and the vent checked. It almost seems it is something with what American Standard call the "priming", but I ran through their procedure of flushing water five times in a row and that did not correct it. Any suggestions?