cbbackupmgr failed to backup and restore data when upgrade from 2.5.2 to 3.1.6 to 4.5.1

Install Couchbase Server 2.5.2 on 2 centos 6.x servers.

Create default bucket.

Load 20K json docs via cbworkloadgen

Upgrade cluster to 3.1.6 by using online upgrade (swap rebalance)

Upgrade cluster to 4.5.1-2860 by using online upgrade (swap rebalance)

Run backup using cbbackupmgr

Load 20K json docs (cbworkloadgen with new key)

Run backup using cbbackupmgr again to do incremental backup

Load 10K json docs(cbworkloadgen with new key)

Run backup using cbbackupmgr again to do incremental backup

Load 30K json docs (cbworkloadgen with new key)

Run backup using cbbackupmgr again to do incremental backup

Total docs in bucket shows 80K

Create another fresh 4.5.1-2860 (no upgrade).

Restore data to new 4.5.1 cluster.  Only half data (40K) loaded to cluster

Create another repo and archive to do full backup in upgrade cluster.

Delete default bucket in fresh 4.5.1 cluster and restore back data.  It still shows same result, only half data restore back.