The lack of knee bend is preventing you from laying the ball down smoothly. To go along with that, you are definitley hitting up on the ball with a lot of force at release. This may be ok on an easy house shot, but when tougher conditions are out, you want a consistent laydown point and realese point to enahnce accuracy and consistent ball roll.
Slow you timing down and try to keep things more aligned...not so many "moving parts"...as you alluded to with moving your head a lot.