Hi Cab.
I had the same problem & only got around it by
a) my chief culprit egg-eater disappearing whilst free-ranging (we only found a few feathers),
b) building a bigger nestbox to take rollaway nest box inserts,
c) taking down the "curtain" that I'd put up to make the nestbox dark to discourage egg-eating &
d) filling the whole area of coop that wasn't occupied with perches, with flowerpots, so that the only place that the hens could lay was on the rollaway inserts. I also had to put some bedding (aubiose in my case) on the inserts for a few weeks to make them more attractive to the hens, to get them to start using them.
Now the hard-shelled eggs are pretty safe from eating. It's taken a lot of work, but it was better (in my eyes) than culling the egg-eating birds & restocking, as I'm too soft for that.
Hope you can solve the problem. Eggshells filled with English mustard (it needs to be a yolk-colour mustard) placed in the coop can also help, & are well worth a try.
I still occasionally get eggs with an exploratory