There has been a change in between 5.16 and 5.17.x breeze-gtk that lead to the fact that the scrollbars of GTK applications are noch pick-able at the border of the screen. There is a small spacing between the screen border and the scrollbar which is not taken into account and which leads to the fact that you have to pick the scrollbar exactly if you want to move it up or down. In 5.16 this worked fine and as expected.