Sometimes when a movie replaces a director in the middle of production, it works out. Such classics as "The Wizard of Oz", "Gone With The Wind", "Spartacus", and "Jaws" did not end with their original director. The most famous case might be "Superman II", when Richard Lester supposedly saved(?) the film from Richard Donner.
And then there is "The Island of Dr. Moreau", the H. G. Wells classic that was supposed to become a blockbuster in the late 1990s. The one and only Marlon Brando was to portray the eponymous mad scientist. Val Kilmer, just fresh off his success(?) as Batman, was to have a major role. The director attached was someone named Richard Stanley, who had brought the project to Hollywood.
It all started terribly. Brando just couldn't give a damn. Kilmer, known for being difficult, was simply disobedient. The inexperienced Stanley was blamed and fired. He was replaced by veteran John Frankeheimer, who had helmed such films as "Birdman of Alcatraz" and "The Manchurian Candidate".
The result? Frankeheimer didn't exactly help things, creating what is considered one of the worst movies ever: a garbled, pointless, incomprehensible mess that should have never seen the light of day.
If you look up "production hell" in a dictionary, you might as well see a poster for "The Island of Dr. Moreau".