My toilet flush tank has a problem. Any water that goes into the tank goes straight into the toilet. It doesn't even allow the tank to refill i.e. the water just goes right through and into the bowl. It looks like the images attached. When I press either flush button, something below the red caps moves back and forth (and it sounds normal).
I don't really know how this mechanism works and what the problem might be. The building handyman says he needs a part that takes weeks to arrive after ordering. Is this a very uncommon design? This is in London, UK.