bungie
Three things to look for,
One, the washer at the bottom of the flush valve perishes and starts to expand, it catches the edge of the tube it runs through…. change the washer.
Two, some units came out with slight defects on the joint of the molding … use the back of a chisel to scrap away the excess on the joints all over the fitting.
Three, if the flush pipe from the cistern to the bowl is a little to long it puts pressure on the valve, pushing it over slightly, so as the flush valve drags on the side of the unit and will not drop
