I'm on a 2013 Mac Pro running Sierra OS 10.12.3. On my Vita I use vitaShell to mount the drive through a USB cable. I can't eject that drive properly (by clicking the Eject icon next to the drives name) and get the "disk not ejected properly" error every time. Since I'm using a 64gb card - which I've read can be prone to corruption (especially if it isn't ejected properly), I'm trying to find out the proper way to eject this drive - even if the solution is a Linux command in Terminal that is fine for me. I've tried two different Mac's on Sierra. The Vita ejects properly every time on a 2009 Mac Pro running El Capitan OS, FYI.