I'm having an odd problem and wonder whether anyone else is experiencing this. For 2-3 years I've had 3 backup schedules: Hourly, Daily and Weekly backing up to an external usb drive. Lately when I open the admin console to cheque the status of the backups it's giving me a folder not found or aborted unexpectedly error message. When I edit the schedule sure enough it reports not a valid path. It is a valid path. So I close all files and restart the server machine (Mac mini OS X 10.11.4). Then the schedules run fine. After a day or two the errors come back and I have to do it all again. There is an OS account logged in at all times so the usb drive remains mounted. Of course a password is required to wake from display sleep. Computer is set to never sleep. Same with the drives. Any ideas?