[Dovecot] Duplicate Messages, Different X-UIDs?

We're running into an issue where sendmail is only receiving one e-mail, but after a client accesses the message via IMAP and moves it to another IMAP folder, the message duplicates but each message has different X-UID headers. Has anyone ever seen this type of anomaly before? Is it a bad IMAP client, or a known bug?

Running 1.0.7

Thanks!