STATUS_GET_LAST_MESSAGE should always return the last message that was sent.
STATUS_GET_LAST_MESSAGE is used to handle the situation where a Status or Queued message is lost or corrupt. If the controller is issuing "STATUS_GET_LAST_MESSAGE" it's because it believes the previous message was not delivered properly. Thus, the responder needs to re-send the previous message to ensure it's delivered properly. Otherwise that message could be permanently lost.
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