Ah, I understand. You mean when you click above or below the scroll thumb *without* dragging the mouse. Yes, this is a problem. Something has changed in the way Qt 5 manages these mouse click events, with respect to Qt 4 (used by PI 1.8.3). I'll see if I can revert this change by modifying some property of QScrollBar, or will manage these events on my own otherwise, to force page by page scrolling. Thanks for reporting this problem.