There are a number of reasons this happens, alignment MAY be one. The most common, in my experience, is where our mind is at the time of release. IF you are thinking about getting your fingers off the string, then I think you are thinking about the wrong thing.
But IF you think about either the string arm elbow OR the string side shoulder and using a horizontal (towards the back) movement, not a downward movement, then you are setting up for the string hand to move straight back. Think about the shoulder or elbow and NOT the hand!
I've suggested many times that the follow through is not something YOU DO, it IS something that happens. Your hand dropping sounds like a long term habit and will take a fair amount of time to correct, if you decide to.
To be more specific, would really have to see the shot execution. Video?
Arne