Once you identify them, remove them from the flock permanently. That is how I handled it. They learn from each other. Sometimes it is one hen that cracks the egg, then some others join her in eating the egg. But before too long, the others start learning to open the eggs themselves.
You can build rollaway nest boxes. You can try a search in here or maybe try Google. With these, the egg rolls where the hen cannot get to it to eat it.
Some people claim success in breaking them by putting weird stuff in an egg for them to eat, like hot mustard, or putting fake eggs in the nest so they are pecking on wood or something hard when they try to eat one, combined with gathering the eggs real often. I've never tried this so I can't say how successful any of this is.
Good luck!