I do that too when I release before I am at anchor. I sort of jerk through the last part of the draw and if I let go just at that wrong spot my finger tear at my cheek. If I concentrate on my follow through I get my thumb under and behind my jaw bone, then when I release properly, my fingers tips go forward a bit and my arm goes back a bit, which equals to my fingers staying on my anchor point. It's all easier said than done.