Symptoms
- You have set up a Disks backup. The initial backup (and the following incremental backups, if any) worked correctly
- You install an upgrade to macOS.
- When you try to run an incremental backup after macOS upgrade, the operation fails with:
The last backup has failed. No current partition
Cause
macOS upgrade changed the unique volume identifier for the source disk, while the backup task configuration still refers to the old volume identifier.
Solution
Re-select the backup source: click on backup source icon, select the necessary disk(s) again, and click Back up
This issue does not reproduce if Entire Mac is selected for backup: please consider this backup strategy if you face this error multiple times.