Following an earlier thread on flap open or flap closed we changed to flap open. Unfortunately a small leak on floor around the foot of the bowl alerted us to a problem. Removed cassette and found the floor of the unit was awash! I am assuming flap was not fully open and this allowed fluid from the bowl to leak around the junction of the bowl and cassette. Reverted to flap closed and not had any problems since. Hopefully that was the issue and there is not a problem with the cassette flap seal.