[Dovecot] Sync errors trying to sync old mbox inboxes to dovecot

[Michael Smith]

We are currently running dovecot 2.2.rc3.

I am trying to 'dsync mirror' old Qpopper/mbox inboxes to our new Dovecot/mdbox servers.  For most of the several thousand accounts, it works without issue.  But there are a handful of accounts that are generating the following errors.

dsync(joe): Error: Sync failed for mbox file /var/opt/migrate/users/joe/inbox: seq=981 uid=981 uid_broken=0 originally needed 9 bytes, now needs 11 bytes

dsync(john): Error: Sync failed for mbox file /var/opt/migrate/users/john/inbox: seq=115028 uid=115028 uid_broken=0 originally needed 34 bytes, now needs 35 bytes
dsync(john): Error: Sync failed for mbox file /var/opt/migrate/users/john/inbox: seq=114779 uid=114779 uid_broken=0 originally needed 34 bytes, now needs 35 bytes
dsync(john): Error: Sync failed for mbox file /var/opt/migrate/users/john/inbox: seq=114778 uid=114778 uid_broken=0 originally needed 34 bytes, now needs 35 bytes
dsync(john): Error: Sync failed for mbox file /var/opt/migrate/users/john/inbox: seq=114621 uid=114621 uid_broken=0 originally needed 34 bytes, now needs 35 bytes
dsync(john): Error: Sync failed for mbox file /var/opt/migrate/users/john/inbox: seq=114610 uid=114610 uid_broken=0 originally needed 34 bytes, now needs 35 bytes
dsync(john): Error: Sync failed for mbox file /var/opt/migrate/users/john/inbox: seq=114607 uid=114607 uid_broken=0 originally needed 34 bytes, now needs 35 bytes
dsync(john): Error: Sync failed for mbox file /var/opt/migrate/users/john/inbox: seq=113993 uid=113993 uid_broken=0 originally needed 34 bytes, now needs 35 bytes
dsync(john): Error: Sync failed for mbox file /var/opt/migrate/users/john/inbox: seq=113868 uid=113868 uid_broken=0 originally needed 34 bytes, now needs 35 bytes
dsync(john): Error: Sync failed for mbox file /var/opt/migrate/users/john/inbox: seq=113855 uid=113855 uid_broken=0 originally needed 34 bytes, now needs 35 bytes
dsync(john): Error: Sync failed for mbox file /var/opt/migrate/users/john/inbox: seq=46725 uid=46725 uid_broken=0 originally needed 32 bytes, now needs 34 bytes

What exactly is this error indicating and how can I fix it?