This is on Windows Server 2012R2 Essentials specifically. But I saw the same behavior on 2012 Essentials before switching.
Both on the Dashboard's alerts and daily health reports, it indicates that one or more drives are unhealthy and need to be fixed. However, it does not list any disk specifically. This occurs several minutes after the backups are scheduled, and will change when it happens if I change the time for the backups.
This happens EVERY DAY. Deleting or ignoring the reports just cause it to come back. Disabling backups, or disconnecting the drive they're stored on doesn't fix it. Neither does formatting the drive and setting up backups again.
I've not found any specific errors, and I've scanned the system partitions using their volume ID, and that hasn't helped.
No virus scanner nor disk tools are installed. There are no 3rd party file system filters installed either.
The Event Viewer doesn't indicate any issues specifically either.
This is frustrating and annoying.