I intentionally installed libproxy1-config-kde4 and KDE desktop effects preview crashed all KDE settings dialog. Then I installed libproxy1-config-kde from http://download.opensuse.org/repositories/home:/dimstar:/branches:/GNOME:/Factory/openSUSE_Leap_42.1/ and it replaced libproxy1-config-kde4. KDE desktop preview no longer crash at during desktop effects preview. Thanks!