Not Getting on Top

every now and then when i’m throwing my fastball it seems like i’m throwing a cutter because i can’t seem to stay on top of the ball consistently. which is why my to seem moves maybe a centimeter and pronation is even harder than what it would normally be. so my questio is this, is there something i can do prior to releasing the ball that would help me to stay on top of the ball?

Adjust your grip so thumb and middle finger cut the ball in half.