I can open Siri or Alfred via keyboard shortcuts, but neither receives keyboard focus or reacts to the mouse. I can bring up the Cmd-Tab switcher and select a different window, but doing so does nothing – the app that had focus keeps focus, and the windows stay as they were. I can't bring up any menus, get the “Force Quit” window to appear or change active windows. And after that, the window manager appears to be frozen. What happens is that the windows start moving inwards (like they do for Exposé) for a beat, but then stops again almost immediately. I don't use Exposé very often, but some times, when I trigger it accidentally with a swipe on the trackpad, it freezes the window manager. On my MacBook Pro (Early 2015), I've been struggling with a problem since I upgraded to Sierra.
