Some time ago I found that when I tried to eject any external drives  from my Mac it always failed on the first try, but succeeded on the second.

This is very annoying, as I’m using alfred to speed up pretty much every command on my Mac. So basically I had to type “eje” (the start of the Eject command) two times instead of one..

It turned out that CleanMyMac checked the drives as they where being unmounted, thereby locking the drive. So I disabled these settings and voila, everything worked.