Hambone
Ain’t she pittyful
Honestly it’s just a side effect of manufacturing. Any time a chunk of steel gets heat treated there’s no guarantee of a perfect outcome. It’s position in the oven could’ve changed how hot it got. Even how quickly it cooled off. Files are typically mid 60s Rockwell so they can cut 99% of materials out there. It takes an exact science in order for perfection to be produced. It’s unfortunate that you happened to find the odd ball but the replacement should be good to go.