For one login, the keyboard shortcut Command+E flashes a LibreOffice window (I've installed it) instead of opening Files. But for another login, the shortcut opens Files OK. As far as I can tell, the shortcut has been defined the same way for both logins ... but there's obviously a difference ... which I can not pinned down: any help would be appreciated !
You can see what system keyboard shortcuts are set up on your system by looking in System Settings/Keyboard/Shortcuts. On my system
<Super>E launches a new Files window because I have a custom shortcut set up which runs
io.elementary.files -n ~. Variable results from the same action suggests a race between two processes both responding to the same shortcut.