Try defragging in Safe Mode. To do this reboot and keep tapping the F8 key just before the Windows screen appears. Then select Safe Mode from the menu which should appear.
Doing this will stop processes running that are interfering with defrag.
Motorola Moto G6 review: Hands-on
The best smart speaker: Apple HomePod vs Google Home vs Amazon Echo
Les meilleurs jeux gratuits pour Mac (2018)