Issue with eOffers not being sent or creating a transition

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We are on 13C (but also experienced this issue on 12C) and are using eOffer (Advanced setting) with Transitions.  We have intermittent issues where we extend the offer, but the eOffer email to the candidate is not sent and no transition is created for the candidate.  In most cases, if we rescind the offer, create a new offer and extend again it will generate the email and the transition (although sometimes this may take 3 or 4 tries).  Is anyone else experiencing this type of issue?