Spurious repeated download of thousands of messages

[Jacek Generowicz]

Hello,

Sometime today offlineimap started downloading over 2000 messages from
one of my IMAP servers, only to delete a similar number immediately, on
each and every sync.

The end of one of these sequences looks something like this:

 Copy message 605763 (2438 of 2440) PersonalRemote:INBOX -> PersonalLocal
 Copy message 605764 (2439 of 2440) PersonalRemote:INBOX -> PersonalLocal
 Copy message 605765 (2440 of 2440) PersonalRemote:INBOX -> PersonalLocal
 Deleting 2440 messages (600882:603321) in Maildir[INBOX]


Could you suggest how I might go about debugging this situation?

Thank you.