[Dovecot] FETCH for mailbox INBOX UID 39641 got too little data: 4823 vs 4825

Whenever I try to access an e-mail in the middle (rather than at the end) of the mailbox, my mail-client (KMail) gets an error a message like this is logged in the maillog:

IMAP(mi): FETCH for mailbox INBOX UID 39641 got too little data: 4823 vs 4825 IMAP(mi): Disconnected: Disconnected

The actual numbers vary, but it is always X vs X+2

The problem started when I upgraded to 1.0.8. Unfortunately, it is still here with 1.0.9. The mailbox in question is the standard Unix mbox (/var/mail/mi in my case).

The server runs FreeBSD/amd64. Please, advise. Thanks!

-mi