I have to click the "scroll down" button in a table several times until the table scrolls down one line.
The number of times you have to click the button is not constant.
I did some more debugging: The problems seemst to be the animation of the scrolling.
In the "_animateTo" method of "qx.ui.form.Slider" starts an animation sequence, that never ends.
So the on "end" event listener in the "_animateTo" method is never called and the table never scrolls down to its intended position.