I get this:
... when (successfully) running this:
/usr/sbin/diskutil unmountDisk disk1 > /dev/null
I added the output re-direct to /dev/null to absorb the success report from diskutil. However I get the same error from FS whether the output re-direct is included or not. The Console contains only reports from FS that the disk was successfully unmounted.
Any ideas why FS might be throwing an error would be much appreciated.