Possibly the extra washer (spacer) was left out between the prop and bulkhead or the spinner filler was not flush with bulkhead. Or the prop stop setting allowed to much travel. Have seen a prop with a 1000 hrs on it with no mark sent in for OH, reinstalled and after a few hours a wear mark shows up. Very important to check this clearance with blades turned to the stop. Easier done if a couple of arms are made out of wood or adjustable slider clamps with protection are used.
The three that I seen were not so deep and were repairable. So sad to see!