Eject button in Finder does not work Every now and then (it seems to me especially after TM backups, but that is about the only reason I plug them in), I am unable to eject and external hard drive by clicking the eject button in Finder (it simply does nothing). It works when initially plugging it in, but not after the backup.
I can however eject it by right-clicking and choosing Eject, no problems.

This happens with two different drives I use for backup.

Has anyone else experienced this issue or can suggest what the problem might be?

My OS is 10.10.3
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.