There seems to be a problem when you size the window down
to be very small. The scrolling up is ok but scrolling
down is broken.
To redo this bug try this.
Size the window down from the top down so that you have
it very small and try to scroll. (Here is when you
can't scroll down only up)
Then after this, try to resize it up slowly and try the
scroll up and down. At one point the scroll works fine.