I have a Geberit dual flush concealed cistern (jpg file attached) in the bathroom that has started leaking very slowing into the toilet. My stupid question is "how do I get the flush plate off?" I have tried sliding it up, down, left and right in the hope that one edge will lift clear, but so far with no success. (It does only seem to move up, I just tried the other directions.) It could be I am simply not using enough brute force and ignorance, but would appreciate somebody who knows giving me a clue before I actually break something.