Toilet cassette flap.

IanH

You know that flap on the cassette? The one that gets opened when you turn the handle on the toilet?

Well, ours has become very loose. It used to be held in place by friction by the rubber seal around the hole through the cassette. But now, when I go to empty it, the flap is in danger of falling off. I dread it falling down the drain.....

Why do you think this is? Can it be returned to its former self?