Everyone was careless: COR, Beaufort, Nobilis, and most of all, Calissio. The root problem seems to have been that Calissio believed it only owed the dividend on stock issued and outstanding as of 30 June. It was wrong about that, and so it underfunded the dividend by quite a lot.
Worse yet, in the end, it actually COLLECTED dividend payments--$4 million worth--on the stock sold to it or its affiliates by Nobilis and Beaufort.
And COR was left holding the bag. The mystery to me is why DTCC didn't hold Calissio's feet to the fire, rather than COR's, since it was Calissio that underfunded the divvy. But then COR has an account with DTCC that can be debited. Calissio doesn't.