Suddenly all on the same date, 3 of the 13 would not boot, "reboot and select proper boot device"  Bios does not recognize hard disk.  Tried 3 sessions with Acer support to explain this and they were rude, snarky, and could not provide any help other than copy / paste to some generic links.  I'm sure it's some BIOS or SSD firmware issue but Acer doesn't apparently support their products.  You are on your own!