Once a hen gets a bad habit of egg eating, the chances of rehabilitation are slim. There are many, many posts and threads here on the subject. If they eat a dropped or broken egg, chances are that is just instinct and won't result in future issues. But the deliberate egg eater must either be changed or culled.
Not laying in nesting boxes was the initial difficulty in this scenario. Gotta get those pullets laying where they are supposed to be laying. Find out who the egg eater is and get her out of the flock, would be my advice. The habit can be taught to others.
There are a few things you can try.
Filling out blown out eggs with hot mustard, horseradish or liquid soap. The idea is that they won't taste good.
Keeping the nests/coop dark so that they can't see the eggs. Some people have put curtains in front of the nests.
Collecting often
Fake/inedible eggs in the nests.
Pulling the ringleaders out, seperating.
I had success by rearranging things in the coop.
There is limited success with any of these techniques, but might be worth trying.