Other mistake: After hitting the "Delta block", Magnum tells Laura about it. The footage that opens the scene is taken from a previous episode, 1-3 "China Doll", around 00:35:00: same girl in orange bikini showering on the beach, same couple walking by the surf (he has kaki shorts and a blue hat, she is wearing orange).(00:12:00)
Continuity mistake: When Magnum drops the ring out of the envelope, nothing is near it as it's shaking. In the close up shot, it's next to keys.(00:44:20)
Higgins: How fiendishly deceptive of you, Magnum. I could have sworn I was hearing the emasculation of a large rodent. To my great surprise, I see the sounds are emanating from what I thought was a harmless musical instrument. Magnum: Cute Higgins, real cute. Higgins: Why Magnum? Why do this terrible thing? Magnum: Higgins, I'll have you know I used to be very good. I was the second best sax player in my High School band! Higgins: Well, how many sax players were there?! Magnum: ...Anyway. I just saw this in a pawn shop window and thought I'd like to try and get my chops back. Higgins: May I suggest that your "chops" are irretrievable. Magnum: Higgins, did you come here just to abuse me!?(00:05:25)