Our GLD has done this a couple of times, on the latest firmware and the previous version.
It will freeze when “Power down?” “Yes” is pressed, then 5-10 seconds later it will reboot to the grey “Not shut down correctly” screen. It will work normally from here and will power down properly.
It shouldn’t be doing this, but as long as it only freezes when I’m trying to switch it off I’m pretty happy. []