XFCE4 Session Manager (Chooser) Does Not Recognize Keystrokes

On one of my Kali laptops XFCE4's Session Manager (aka Chooser) shows two sessions. Normally, when you want to start the highlighted one, you just press ENTER and that's it.

But on this laptop the Session Manager simply does not react at all. Luckily, the touchpad is already active in this state so I can start the session using the touchpad and its buttons.

After the session has been started, really everything works fine.

Any ideas in which direction to look for a possible reason?