Using Natural Scrolling via xinput http://askubuntu.com/questions/411034/kubuntu-natural-scrolling-touchpad-only-but-not-for-mouse/416542#416542 When scrolling large texts rapidly, the scrolling occasionally for a split second goes the wrong way, even if the wheel is constantly rotated in a single direction This is most apparent in a 10-window high or larger page in Chromium when constantly scrolling towards the bottom. Instead of constantly moving towards the bottom, the scrollbar occasionally stops and sometimes goes a little bit the other way. The touchpad works fine.
In Chromium, it is also visible at the very bottom of the page, when the page "bounces back" upwards instead of being held firm at the final scroll position
The bottom edge symptom is also exhibited by LibreOffice Writer
This was caused by a faulty mouse replacing it with another same make/model removed the problem https://bugs.kde.org/show_bug.cgi?id=372556