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The Preliminary CD (as my company calls it) is required to be delivered at least 3 days prior to your Closing or RESPA requires your closing to be postponed.
Unless anyone has already "dropped the bomb" on you regarding any other trouble your "buyers" are having it's likely to be no big deal and business as usual, but certainly reach out to your Agent so they can get in touch with the Buyer's Agent to ensure everything is copacetic.