Might be related to https://bugs.kde.org/show_bug.cgi?id=324438 as changing the GTK2 Theme in KDE to something other than "oxygen-gtk" seems to fix the problem here...
Might be related to https:/ /bugs.kde. org/show_ bug.cgi? id=324438 as changing the GTK2 Theme in KDE to something other than "oxygen-gtk" seems to fix the problem here...