Have never pulled mine apart but had an issue early on in the ownership of my Giotto.
I was basically cleaning it to death, doing a clean and backflush once a week with the caffetto but because my consumption of coffee was not high, only 30 shots per week i had actually started to destroy the lubricant around the mechanism. The lever would get harder to operate to the point that it basically felt like metal on metal as i tried to pour a shot.
The unit went back to Chris at Talk Coffee who pulled it apart and re packed the area with food grade grease and all was well again. I now only clean and backflush once every 2 weeks and have been doing so for more than 12 months now and everything is working well.
I didnt realise that over cleaning would have a negative effect on the machines operation, but it does make logical sense when you consider that the cleaning is designed to remove the buildup of coffee oils so i guess too much will destroy the lubricants as well.