A common error that we see is "Duplicate status message" when an institution posts a general closing or even a test message.
As the text name in the error implies, this FB error indicates that Facebook has rejected the post, detecting it as a repeat of a previous post on that Facebook Page.
How can you avoid this error from Facebook?
Facebook does this filtering by an algorithm on their end. It's intended to stop "spam" on their site and is not something that you or Omnilert can override.
As you can guess, you must always be sure that your posts to Facebook are uniquely worded to the situation. Posting a "generic" status that is similar to something you may have posted previously is more likely to get your post blocked by Facebook's system.