[opensuse-gnome] unusual scroll behaviour in SLE12

Whenever someone is working on this SLE12SP2 desktop there is a huge surprise when the scrollbar is used in LibreOffice or Firefox. The expected behaviour is that a single click scrolls down exactly one page, instead of jumping down to a random location. YaST and chromium, as Qt applications, show the expected behaviour. Looking through the "tuning app" there is appearently no GUI knob to fix the bad behaviour. Olaf