My toilet is equipped with a Geberit Sigma 70 flush plate. The sales pitch for this hydraulic-assisted device praises the “ingenious mount that acts like a rocker switch.” In practice, the flush is very capricious and has a very high failure rate. Avoid this type of mechanism! Prefer a fully mechanical version like the Geberit Sigma 20.
After several plumbers, exchanges with Geberit’s technical department, and the expensive replacement of the entire mechanism, I was still getting a failure rate of over 50% for the small flush. I finally managed to decrease this rate to 5% by applying two 8 mm silicone bumpers on the back of the plate. Their locations are indicated by red circles on the picture below:
Expect to pay about 5 € and as many minutes for this operation.