This sounds like operator error. IF it will focus accurately when you activate the AF system it's fine however it's been set (microadjusted). If it was soft after activating the AF then it hasn't been microadjusted accurately. You must de focus between each test shot when doing this. You might also want to try doing it this way
http://www.fredmiranda.com/forum/topic/1187247
"A skill is developed through constant practice with a passion to improve, not bought."
