If you got instant refund that's because of reason 4. likely, that your post wasn't voted by anyone else yet. We are thinking to remove that limit so that there can be more time for curators to evaluate post. Instant refund happens because of these checks, previously we had refund after 24 hours if post somewhat missed out of curation list but we changed it into instant so that it will give user direct feedback and you could always re-try.