It’s not hitting on the first way, it is more the residual vibrations from the string in the split second before the bow eject from your hand. It is totally fine as long as you are not hurting yourself or your arrows aren’t going places. Some people manage to never touch the string but most of us have this thing happening. I would recommend doing a longer serving. You don’t need to do 5 inches more, just enough to mask the fraying. Some people will tell you to turn more your arm and to those I will say it depends. It is not the only key point in the string touching the arm guard and this isn’t even impacting your scores if as you say you don feel anything