I want users to be able to control my app with Siri voice commands, even (and especially) when it's not running.

The phrases I have defined in my AppShortcuts work reasonably well when the app is running, either in the foreground or in the background. But the moment I kill the app in the app switcher, Siri doesn't understand me at all. It does not execute the respective AppIntent and starts a web search instead (or does something completely different thing like playing music).

What might cause this behavior and how do I fix it?

Below is one of my AppShortcuts as an example.

AppShortcut(             
    intent: OpenAndStartTimerIntent(),             
    phrases: [                 
        "Restart \(.applicationName)",                 
        "Restart the \(.applicationName)",                 
        "Restart the timer in \(.applicationName)"             
    ],             
    shortTitle: "Restart Timer",             
    systemImageName: "arrow.up.circle.badge.clock"         
)