Scrolling gone haywire

[Go Canes]

I'm trying to convert my wife's laptop from Windows 7 to Fedora 22 running
KDE 5.  However, when she browses the web, occasionally the page will
scroll as fast it can - either up or down - with no input on her part,
other than loading the page.

The problem occurs with Firefox, Seamonkey, and Konqurer using KDE 5.

The problem does *not* occur at all under MS Windows 7, again using Firefox.

The hardware is a Dell XPS-13 laptop, originally came with MS Windows.

I have googled around, but haven't found anything that sounds similar.  I'm
planning to see if there is enough space to load Gnome and see if it also
exhibits the same behavior.

Any suggestions for additional troubleshooting?