I think you have to decide which came first here---the prevention of the release by B1, or the shot clock buzzer. Since the buzzer occured "at the top of the jump," if there had been no buzzer, there still would have been a chance that A1 could have released the ball on her way down to the floor. So, I'd say that the shot clock violation occured first. Ball to B, arrow stays with A.
I'm probably wrong, too.
