I put fake eggs in and eggs were still being eaten....so I took a fake egg and a real egg in my hand, walked into the run, rolled the fake egg on the ground...all the hens went for it and pecked it, waited until they were done, saw one hen was more persistent.....then rolled the real egg and all of the other hens could care less since they just chased the fake egg but the one hen went after it, worked on it until it broke then started to eat it....put her in a stall and did the exercise again in the main run...the hens all went after the fake eggs, quickly lost interest, tolled the real egg, then looked it over and ignore it....got rid of the hen and no more egg eating from hens again (knock on wood)....I had to let them try to eat the fake egg first and with the second real egg, I knew the egg eater would be persistent.
I have also waited until the eggs were laid, then let the egg eater break the egg, then rush in and see who had the wet beak....sometime the other hens would join in but the egg eater would have yolks all the way up to her head.....
so now, I have the nest boxes loaded with fake eggs and if I do get eggs eaten, it is due to weak, thin shells....I add more supplement/shells and the problem fixes it self.
Sometimes I can break the hen but if they still continue, then it is bye-bye for them. I had advertised them on craigslist for $5 each, as egg eaters, hence the reason so cheap, and a lady snapped all of them up. There were four sisters (hatchery RIR) who ate eggs from day one and would not stop. She bought them knowing they were eggs eaters and I told her I tried all ways to get them to stop....ran into her a couple years later and asked how she did (as she was going to break the egg eating habit)....she told me that she cured them of egg eaters...I asked how...she said the coyotes cured them....she never was able to stop them either.
If I catch it early enough I can break them, but they make it a habit, sometimes they will have to go bye-bye. Mine have free choice of food, shells, grass, corn, bread, etc so it's not a matter of lacking something.
Knock on wood, now I have a nice flock that lays eggs and eats bugs, not eggs.