Why won't my G-Drive Slim eject from Mac Finder?

I have a G-Drive slim external drive that I use to store my time machine backups. I've had it for nearly 10 years and until recently, ejecting it from Finder worked fine unless a backup was in progress. Lately, it will not eject. I have tried shutting down all applications and restarting the Mac, but it has no effect. Could the drive be developing a problem and heading towards failure because it is old?

[Re-Titled by Moderator]