I do not understand how could Bialetti coffee out with such a design problem. It's sad and do not complain if people are going to like Nespresso coffee makers (coffee not very good but easier).
I was able to cobble something together to address the issue. I plugged the hole in the top of the handle with heat resistant resin (type to plug the leaks in the drinking water pipe): Now the coffee no longer flows but it is ugly because of a large white patch.
In short, these coffee makers make excellent coffee, but I do not recommend buying this model as Bialetti does not return to the drawing board.