[Dovecot] Migration to mdbox from Maildir, missing folders!

So I went and migrated a mailbox from mdbox from maildir format.

All seemed ok, but I've found that I now have some missing folders.

The mailbox in maildir format had some folders which contained an '&' sign, these appear to have been omitted...

What can be done? (I have a backup of the maildir box).

Note though that mdbox is now a live mailbox and has sent and received mails since the migration...

-- Message sent via my webmail account.