I used to think I just messed up some shots and now I can see that most of the time number 3 hits 1-2 inches to the left or number 7 hits low 9 out of 10 times
If the arrow is straight and spine is the issue try twisting the nock and then recentering it to how every you shoot(cock feather up,down,out). Sometimes a slight adjustment will change the spine of the arrow and help it to shoot more consistantly.