clicking on corresponding icon gives nothing. The reason is printed into console: systemsettings: Unexpected argument '%i'. systemsettings: Use --help to get a list of available command line options. systemsettings works just fine when executed manually, so xfce4-settings should call it with correct options. Also if call fails for whatever reason user should be presented with error message in gui instead of silent failure.
This is not a bug in xfce4-settings, as it doesn't add parameters to the calls itself. Rather this would have to be fixed in systemsettings' .desktop file.