If you upgraded from a previous setup of Windows to Windows 10 and had been making scheduled backups, you should know that Windows 10 will back things up twice: Once using Backup and once using File History.
Nowhere is there any UI element warning or alerting you to this behavior. In other words, if you set up File History, nothing asks “Do you still want to use Windows Backup?” or vice versa. During Windows Setup there should be something to migrate from Windows Backup to File History.
I am calling this a bug since it degrades performance without any benefit as it will cause your backup space to deplete much quicker for no benefit.
I recommend either ignoring File History and keeping the old Backup running on schedule OR disabling the Backup schedule and just using File History. I’m using File History, but that’s up to you.