I had an egg eater also. Sometimes they can be broken by using the above techniques. I had great success by blowing out the yolk and putting a hot sauce inside. Put that egg back into the nestbox and wait. I found that egg broken open with the hot sauce spilled out... never had another egg eaten since then. I only had the one hen eating eggs though so that helped.
Sometimes they cannot be stopped and you have to cull them; or take a chance on other hens learning that behavior from them - that's a bummer because you start to lose most of your eggs.
Sometimes they cannot be stopped and you have to cull them; or take a chance on other hens learning that behavior from them - that's a bummer because you start to lose most of your eggs.