original version of couchbase in which the backup was taken : 6.0.3
version of couchbase used in the test ; 7.1.0-1027 
error seen in the test : 

08:07:16 2021-06-21T19:37:17 [INFO] Running: /opt/couchbase/bin/cbbackupmgr restore --archive /fts/backup --repo fts_geo --threads 24 --cluster http://localhost:8091 --username Administrator --password password --disable-ft-indexes --disable-gsi-indexes
08:07:18
08:07:18 Fatal error: run() received nonzero return code 1 while executing!
08:07:18
08:07:18 Requested: /opt/couchbase/bin/cbbackupmgr restore --archive /fts/backup --repo fts_geo --threads 24 --cluster http://localhost:8091 --username Administrator --password password --disable-ft-indexes --disable-gsi-indexes
08:07:18 Executed: /bin/bash -l -c -o pipefail "/opt/couchbase/bin/cbbackupmgr restore --archive /fts/backup --repo fts_geo --threads 24 --cluster http://localhost:8091 --username Administrator --password password --disable-ft-indexes --disable-gsi-indexes"
08:07:18
08:07:18 =============================== Standard output ===============================
08:07:18
08:07:18 Error restoring cluster: cannot read backup config: backup config at '/fts/backup/exportFiles/backup-meta.json' not found
08:07:18
08:07:18 ================================================================================
08:07:18
08:07:18 Aborting. 

Link to the job: http://perf.jenkins.couchbase.com/view/FTS/job/atlas-sdk/13622/
Link to the cbcollect logs:
https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-atlas-sdk-13622/172.23.99.211.zip
https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-atlas-sdk-13622/172.23.99.39.zip
https://s3-us-west-2.amazonaws.com/perf-artifacts/jenkins-atlas-sdk-13622/172.23.99.40.zip