[Dovecot] UID and status lines combined?

In a couple of mailboxes here I've see a condition where messages get a header like this:

X-UID: 5X-Status: D

I discovered this after seeing this error in the log file: Error: IMAP(glass): mbox sync: UID inserted in the middle of mailbox /var/imaptree/glass01/Sent (3 > 2)

The message has this X-UID line and also has a seperate Status: RO header.

I'm only guessing that this line isn't supposed to be combined like this, as later messages in the same mbox have the X-UID and X-Status on seperate lines...

Any idea as to the cause?

• Mike