How to check correctness of restore archive specification

Hi,
we tried to backup/restore a database instance and ran into errors during restore:
Restoring from restore point: backup_snapshot_20210216_133917
Error: Failed to get snapshot metadata files from backup location. If you specified an archive to restore, please check the correctness of the archive specification. Otherwise run backup validation task.
We conducted following steps according to specifications:
1. We ran a backup an exisiting database that resided in a docker container (vbr -t init -c vbr.ini; vbr -t backup -c vbr.ini)
2. We produced a tarball of the resulting backup-directory.
3. We copied and extracted the tarball on the target server, where a database was already created.
4. We ran the restore command (vbr -t restore -c restore_full.ini)
From the error message something with the archive is wrong. How can we check its correctness?
Thanks,
Jordi