* What you were doing when the issue happened
Nothing special, just trying to lock the computer.
* Whether you were able to replicate it a second time by performing the same action
Yes, Restarting Alfred or "Clear application Cache" do not change the behaviour.
Changing the command name, or requiring Confirmation does not change the behaviour. (With confirmation, the dialogue does show up)
Changing the apps name, does stop the app from opening, but still does not lock the device. Changing the name back restores the unwanted behaviour.
* Include any screenshots that might help us
I can share a screen recording if that is desired.
* Include the Alfred version & build number you are using
v3.6 [903]
* Include your OS X version
10.13.3 (17D102)