This error means that the VSS writer responsible for the SQL server doesn’t work correctly. The error itself is rather generic and can be caused by different reasons. One of them is an update of the Microsoft Azure AD Connect client.
If you recently installed this update, the repair of the SQL installation should fix the issue. If you didn’t, still try the below since it might also resolve other issues.
- Go to Add/Remove Programs
- Select Microsoft SQL Server 2012 Express LocalDB (or your actual SQL version)
- Select Repair
Note that it’ll require a reboot afterwards.
If it doesn't help, further SqlServerWriter troubleshooting will be required. As a workaround, until the issue with the SqlServerWriter is resolved, you can create crash-consistent backups by disabling the application-aware processing or setting it to "Try application processing, but ignore failures."