I always thought it was me doing something wrong. I've only had problems "out" with it, but I thought that if you figured out rate and amount of pressure, you never had to "pump". In fact, I've never found pumping to work really. Just standing around and waiting for it all to fill up again was the solution. Embarrassing, yes, but the only way that works (and hoping the whole cycle doesn't start all over again).
This happened to me the first time I went to a public loo, and seems to happen a lot less often in the past two years or so as I've gotten used to things.
We have two buttons on the top of our tank, which works pretty well. I do admit when I first moved here I missed the "flushometer" style of toilet which is pretty common on most public toilets in the States. We even had one in my last flat there. If you didn't need a "heavy flush" you pulled up on the lever, the same as pushing the small button on our current loo. I am not sure why they had them other than it was a luxury, pre-war building which had been fairly well maintained through the years. They rarely broke, but when they did they were a bit of a pain for the management. One day all the toilets in the building began flushing continuously on their own because of a variation in water pressure.