Raul Julia, nor the role he plays (a key character), isn't credited anywhere in the opening or closing credits of the movie Havana. I have a copy of the film and have run it and re-run multiple times and there is no mention of him or the person he plays anywhere.
It's not a slip-up at all. I remembered Raul Julia was so an annoyed with the film that he asked his name to be removed. His picture remains in the film's advertising though. Why? If you saw the movie, it was a total mess and I was so sorry for Raul Julia that he had to say such stupid dialogue. I was shocked and amazed by the shlock writing. Sadly, Julia passed away soon afterwards.