Cannot unmount external HDD. Only "force unmount" works
Some online games have "helper apps" that update the game in the background. Try plugging in the drive and then unmount it without running the game. If it does work, then you could make a simple Automator/bash script to unmount the drive (it should consist of the two commands you mentioned above, except that you should use sudo killall &lt;appname&gt; for killing the process locking the drive.