I know what happened and it almost happened to me. Marking the holes with the cob in place is hard as the holes on the holder are small, the drill but wants to walk and you can't see where the fins are behind the cob. It's not a big deal to move it over or turn it. If you have a small philips screw driver you can make a small impression to help the drill bit from walking too. This isn't an easy thing to do.