Trap nests helped me find my egg eater too. Only it was a rat. I'd never have figured it out if I hadn't been checking the boxes so often, though. The darn thing was waiting for the hen to finish laying and then run in there and eat the egg! I still have some fine tuning to do because sometimes one of them doesn't trip the door. I'd go in there and see a hen on the nest and the door still open, think about coming back in 30 min then forget for an hour and go back to see no egg! No trace of an egg, nothing. And different hens, not the same one. Only then did it click that I was seeing a rat in there during the daytime, which I never had noticed before. I surprised it a couple times now waiting hidden behind the other nest box that they don't use. So now we're de-ratting the place lol.
I pulled apart the contact cement that I'd used to make a 1/2 inch thick lower door, making it 1/4 again. The lighter door really works much better. And I've found too that having the nail directly under the hinge is the key to getting that part working right. It wasn't working at first because the hinge was effectively 1/2 inch or so in front of the nail. By cutting notches in the front corners of the lower door, I put the trigger point directly over the top hinges and now it works much better.
Another thing I did was make the top section of the door longer by simply using longer strings for the top hinge. It seems that having the door make a V like the Belgian Marans Club doors rather than more of an L is more effective in getting them to trigger it. This is because the hen's back hits the joint in the door rather than the front of it I think.