This will take some explaining. I have a WD EX4 and a 4TB external drive plugged into it via USB 3.0. From my mac I selected all files (about 4TB) and used the cmd move function to move all files from the external drive to the EX4. After about 5 seconds my mac crashed. After reboot it isn't moving the files and yet I can see them all on the EX4, however they're all grayed out as they typically are during the move/copy function. Now I can't delete these grayed out files to begin again because I get "file in use" message. I've rebooted 3-4 times and am having the same trouble.