Hi all, got a push button flush that was stuck, slow trickle into pan. It is a concealed toilet but has plastic cistern that is slightly accessible. Took cover plate off and couid unfree flush valve by pushing a black lever which is just visible in the photo at the back, back down. Works OK now, but is it best to put new flush valve in, or would a new button and cable work? It is just getting slightly stuck I think not sure if cable is vacuum operated and is sticking.