Fix: Two of the disks to back up have the same name. (Time Machine)
If you upgraded to macOS Catalina 10.15 and use Time Machine, you may receive an error trying to back up your disk for the first time.
Time machine couldn’t complete the backup to “”
Two of the disks back up have the same name. Rename one of the disks named “”.
While some suggest deleting the 2nd partition macOS Catalina creates (Macintosh HD – Data), you should simply rename the partition to something like “Data”. Once you rename this partition, Time Machine will back up to your disk. Keep in mind, Time Machine will actually be backing up the “Data” partition, so it will need to remain mounted.