Alt + Tab Bug
I am not sure if this is the correctly location to file this bug. I have seen this for years in Mint's custom XFCE interface and recently in Fedora's XFCE spin.
Alt + Tab does not work correctly for some applications like League of Legends ran through Lutris. The full screen will not let Alt + Tab change the focus to something else. The GUI for changing focus pops up but the focus stays on applications that can lock up the focus.