Other mistake: With episode 11, "Thicker Than Blood", the opening changes to the truly iconic version associated with the series, with a large overhaul of footage. There must have been some hiccup making it though, because the title of the series appears as "Magnum PI", no punctuation. There's a version of the opening that includes the correct "P.I." title card.
Magnum, P.I. (1980)
1 other mistake in Season 1 generally - chronological order
Starring: Tom Selleck, Roger E. Mosley, John Hillerman, Larry Manetti
Revealing mistake: One of the party guests opens the door of the fridge and you can see behind the set instead of looking into the fridge. (00:32:40)
More quotes from Magnum, P.I.
Trivia: At the awards ceremony, three men seated at a table together resemble three detectives from 1970s TV shows. Detective Mike Stone (played by Karl Malden) from ABC's Streets of San Francisco; Detective Frank Columbo (played by Peter Falk) from NBC's Columbo; and Detective Theo Kojak (played by Telly Savalas) from CBS's Kojak. (00:07:20)