I've observed inconsistent behavior in my Drafts folder, Zimbra Desktop 2.0, build 10343.
The problem occurs when responding to a message. Occasionally, messages remain in Drafts after the response has been sent. Typically, the subject is <No Subject> and the message includes my response and the original message.
The problem does not occur consistently and I am not yet able to reproduce it reliably. Are others seeing this behavior?