I had this happen to one of my hens, i caught the offender in the middle of eating the egg while the chicken was trying to laying it, if you have hens that eat the eggs this can be the next step for them as they wait for eggs to be laid, sometimes if they can see the egg they will start before it is laid and then cause damage to the laying hen. I culled the offending hen immediately as I did not want her to start on the next hen. Hens can be canabalistic, I have used purple spray on a damaged chicken, they seem to leave it alone then.