You could buy a game camera and set it up to see what maybe invading your coop and see where they are coming in. You would be surprised at how little space it takes for an animal to squeeze into to get at what they want. Wild animals are smarter than we give them credit for. I have bantam chickens and one morning i went out and all i found left of that one was her head. There was no sign of entry or exit but the bird was gone without any other trace left but her head. It's crazy how wildlife works, but that's how they survive. Very cunning animals.