Engine hesitation and Stall on acceleration

Well I found out what the problem was when I took the fuel pump off I use the screwdriver and could feel that the pump Drive lobe was loose. Took everything apart and I was expecting the bolt to be loose but the bolt was actually tight. it looks like the Woodruff key was getting ground down where the cam Drive lobe attaches not sure how this happened but it looks like all I have to do his replace the key has anybody ever had this happened before? Could the key of been installed incorrectly? Here's some pictures of the key