There is a disorder of the brain called "pica". Heard of it? It afflicts individuals of many different species. The brain compels the body to eat non-food items such as paper, shavings, metal, dirt, etc. Medical professionals don't know precisely why some people and animals engage in this aberration. In some instances it's behavioral, and in other cases it can be sourced to nutritional deficiencies.
Here on BYC, I've seen a few extreme cases of crop disorders where pica was discovered as the cause. When taken to the vet and X-rayed or upon necropsy, gizzards full of screws, safety pins, paper clips, staples, etc were found, and in some instances, shavings.
When a chicken has this disorder, nothing you do will mitigate it. The chicken always ends up dead. This is something you may want to consider.