Other mistake: There is a scene in which Piter DeVries is talking about the Landsraad (one of the governmental organizations in Dune). Twice he mispronounces the name, saying "Lansdraad" instead.
Dune (1984)
Ending / spoiler
Directed by: David Lynch
Starring: Max von Sydow, Patrick Stewart, Brad Dourif, Kyle MacLachlan, Jose Ferrer, Francesca Annis, Sting, Leonardo Cimino
Alia kills the Baron Harkonnen with a poisoned Gom Jabbar. The Fremen capture Arrakin City including the Emperor and his cohorts. Paul is challenged by Feyd Rautha (Sting) to a knife fight. Paul kills Feyd. Paul becomes an Emperor.
Lester
More mistakes in Dune
Reverend Mother Mohiam: I hold at your neck a Gom Jabbar. This one kills only animals.
Paul: Are you suggesting the Duke's son is an animal?
Reverend Mother Mohiam: Let us say, I suggest you may be human. Your awareness may be powerful enough to control your instincts. Your instinct will be to remove your hand from the box. If you do so, you die.
Trivia: The tendons on the worm when it gets hooked by Paul are made from condoms.
Answer: Because it was edited in a way he didn't approve of. The film was actually over 3 hours long, and it was trimmed by about an hour for the cinema version, and then a certain amount of pick and mix went on to come up with the video version.
David Mercier