I too have issues with the latest version, 1.0.1.880, when shutting down, so I try to detach the drives before rebooting. Sometimes I get an error invalid function, other times, the drive will detach, but the drive letter will still exist
Error
[Window Title] Location is not available
[Content]L:\ is not accessible.
Access is denied.
[OK]
In Disk Manager, the disk will have a red X next to it and indicate "Unreadable". Is this normal?