cbbackupmgr failed to restore correct items with --force-updates flag

Install couchbase server 4.6.0-3559 on 4 centos 7.2 nodes
On node 172.23.121.224, create a default bucket and load 10 items to default bucket.
On node 172.23.121.228, create a backup repo named backup
On node 172.23.121.228, do backup default bucket
Update 10 items in default bucket
On node 172.23.121.228, do backup default bucket
Update 10 items in default bucket
On node 172.23.121.228, do backup default bucket
Update 10 items in default bucket
On node 172.23.121.228, do backup default bucket
Update 10 items in default bucket
On node 172.23.121.228, do backup default bucket
Update 10 items in default bucket
On node 172.23.121.228, do backup default bucket
Update 10 items in default bucket
On node 172.23.121.228, do backup default bucket
Update 10 items in default bucket
On node 172.23.121.228, do backup default bucket
Update 10 items in default bucket
On node 172.23.121.228, do backup default bucket
Update 10 items in default bucket
On node 172.23.121.228, do backup default bucket

There are 10 backup times
On node 172.23.121.226, remove any bucket if it was there. Then create new default bucket.
Do restore on single backup file 2016-12-13T07_35_06.232850094-08_00 (backup number 7) to default bucket on node 172.23.121.226

/opt/couchbase/bin//cbbackupmgr restore --archive /tmp/entbackup --repo backup --cluster http://172.23.121.226:8091 --username Administrator --password password --start 2016-12-13T07_35_06.232850094-08_00 --end 2016-12-13T07_35_06.232850094-08_00 --force-updates --no-progress-bar

Verify data on backup file and on default bucket. Both match
Delete default bucket on node 172.23.121.226 and recreate default bucket
Do restore again on node 172.23.121.226 with backup files from 9th to 10th.

/opt/couchbase/bin//cbbackupmgr restore --archive /tmp/entbackup --repo backup --cluster http://172.23.121.226:8091 --username Administrator --password password --start 2016-12-13T07_36_42.38458488-08_00 --end 2016-12-13T07_37_31.452062222-08_00 --force-updates --no-progress-bar

Verify data in backup files and on default bucket => failed due to item ent-backup-0 is not the same on both backup files and default bucket.
Data on backup file:
ent-backup-0aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa (backup 9th)
ent-backup-0aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa (backup 10th)

On default bucket:
ent-backup-0aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

I delete default bucket on node 172.23.121.226 and restore data from backup 9th to backup 10th without --force-updates flag, both data in backup file and in default bucket in node 172.23.121.226 are match.
/opt/couchbase/bin//cbbackupmgr restore --archive /tmp/entbackup --repo backup --cluster http://172.23.121.226:8091 --username Administrator --password password --start 2016-12-13T07_36_42.38458488-08_00 --end 2016-12-13T07_37_31.452062222-08_00 --no-progress-bar

ent-backup-0aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa (restore without force update on actual bucket from 9 to 10)

ent-backup-0aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa (data from default bucket)

Delete default bucket on node 172.23.121.226 and re-run restore with --force-updates flag, there is a different in data in backup file and in default bucket.

All nodes available for debug.