Eject button in Finder does not work
My OS is 10.10.3, and I have both external Time Machine volume, and a secondary external volume.

I also use multiple Spaces with Mission Control, and I sometimes have Finder windows on different Spaces that refer to locations upon my secondary external volume.

When ejecting a volume, I noticed sometimes that the file system will treat the volume as "being in use," apparently because another Finder window was open. However, this behaviour is not consistent.