I shouldnt wear out, I guess it is possible its not dropping as fast. Usualy something has changed on the bow, arrow or vane that causes contact. Im guessing you might be a tiny bit high on your nock point. If thats the case the your nock end of your arrow is actualy headed down at launch which will cause contact. I ran into that problem earlier this year, little bit of string stretch and I didnt notice until I started getting funny flight and black marks on my vanes.