I apologize if someone already suggested this, I did not read the whole thread, but,,,,
We were suspicious of egg eating a couple weeks ago, so we upped the oyster shells (mixed in with feed, as will as free choice dispenser) and, I made some booby trapped eggs!
I blew out 4-5 eggs, and refilled them with Hot mustard watered down with killer jalepeno sauce. (I know that birds taste buds do not get affected by hot foods like ours do, but thier sinuses, and tummies DO) Then, for several days in a row, when I collected eggs, I would switch one, and leave a trap egg behind.
The first day, it was gone by nightfall. Next day also disapeared, third stuck around for more than 24 hours, and the 4th and 5th never got eaten!
I also have stone eggs in the nest boxes, instead of golf balls, and I moved them around daily too.
My egg count has gone up a bit, from 7-10 to 10-12 daily, but that also could be due to the increasing light of the season, and my young girls maturing, so its hard to tell for sure, but seeing those booby trapped eggs sit there untouched made me snicker.
If you buy or have on of those meat flavor injector needles, it is really easy to blow out and refill eggs. We do it for crafts and to save those funky eggs!
Good Luck!