Failed to detect screen is locked sometimes by dbus or loginctl utility when click Lock menu

[chenyu]

Affected version
ubuntu1804.4/20.04

Bug summary
Click Lock menu (especially click lock button very soon after login), the screen is locked as expected. But in this case, there is no org.gnome.ScreenSaver related dbus generated, and less way to report screen is locked. Using dbus-monitor also couldn't be able to recevie the screenSaver dbus message.

Steps to reproduce

Put attached test.sh under /tmp/test.sh
Put attached screen-status-monitor.desktop to /etc/xdg/autostart/screen-status-monitor.desktop
Click Lock menu very quickly after login
Verify /tmp/result, the first "true/false" is to query dbus org.gnome.screensaver.GetAcitve, the second is to query session lock status from loginctl utility, they both indicate "unlocked" status.

What happened
the query result is "unlocked" status

What did you expect to happen
the query result is "locked" status