I haven’t used zypper to update, just clicked on the ‘Install now’ button from the notification.
Tried zypper. Had to ignore two packages which failed, libopenmpt0-0.3.28-lp152.2.3.1.x86_64 and thin-provisioning-tools-0.7.5-lp152.4.3.1.x86_64. Update completed. Zypper showed 261 packages compared to 121 from KDE notification. All now complete.
Better use zypper up or YaST > Software > Online Update in the future. Use that notification applet at the most for just that: notification. Or simply forget (or uninstall) that applet and do, say once a week, YaST > Software > Online Update.