flag provided but not defined: -append

MSR 3.0.3 or later must be running on your target MSR 3.x cluster, otherwise the restore migration step will fail with the following error message:

{"level":"fatal","msg":"flag provided but not defined: -append","time":"<time>"}
failed to restore metadata from "/migration/msr-backup-<msr-version>-mmt.tar": restore failed: command terminated with exit code 1

To resolve the issue, upgrade your target cluster to MSR 3.0.3 or later. Refer to Upgrade MSR for more information.