[dnanian]

From what I can tell, you may have a bunch of bad mount points in /Volumes. Use Finder's "Go To Folder" command to open /Volumes. In there, you'll find one or more folders (not aliases/symlink) with the name of the image. Delete those and empty your trash, then restart your Mac.

The backup "not completing" seems like it's because your network connection is failing, or your NAS is dropping the connection/failing.

As far as "can't eject" goes - this may be because Spotlight is indexing the image, or because an AntiVirus program has active files up there. We certainly don't have active files when we're not running...