No wind, no flying insects, no human error. A strange world some people inhabit.
The wind was blowing the other way, if I'm not mistaken.
There is another video showing the bullet hitting the railing, but from a slightly different angle. It could be interpreted as showing that the puff goes backwards rather than sideways.
However, it does look from the original video as though the bullet hits the back railing (not the side one) at a spot which looks as though it is behind the man standing at the top back corner. So the bullet would have to have hit him if it was coming from Crooks.
There is a ricochet which is seen in the attached screenshot, which is followed by the puff going to the right.