Did You See the Sun Rise? - S3-E1
Other mistake: During the opening credits, the writing "and Lance LeGault as Buck Green" appears. As shown by the name tag later in the episode, his character's last name is Greene with 3 Es. (00:06:50)
Past Tense - S3-E4
Other mistake: Magnum quite literally breaks into TC's office, shattering the glass with his shoe and reaching through to unlock the door. When he and Rick leave, he reaches in again and locks the door back. They get stopped by Lieutenant Yoshi Tanaka in the corridor, have a bit of banter without them touching the door, and when the policemen walk past them, they just have to push the door to open it; it's completely unlocked already. (00:15:55 - 00:16:55)
Foiled Again - S3-E7
Other mistake: The culprit does not have wounds on their hands, but whoever tampered with the box left blood inside it. If the blood is irrelevant to the case and could have been left by Higgins, then it's unclear why it has an effect on the culprit and make them admit their guilt.
Foiled Again - S3-E7
Other mistake: At the beginning of the episode Magnum has some banter with Higgins, but also needs his help with a tie knot he's clueless about, to the point that he can't even pronounce its name and calls it "double Winslow", with Higgins promptly correcting him. And he's completely useless at doing it. However, in the previous season's episode "The Last Page", Magnum was helping Rick with his tie and giving him expert and sensible advice about it and explicitly referencing the Windsor knot, in fact discussing the merits of the half Windsor.
Other mistake: During the airport reunion with father and son, there are several boxes of "Cole" brand pineapples...which are just Dole brand pineapples with masking tape put on to alter the letter D to a C. The tape came off one box revealing the original unaltered letter - you can also see it on the side of a box carried by an extra, Cole on the front, but Dole on the side. (00:43:05)
Other mistake: The supposed teen prodigy at the beginning of the episode hits the balls shot by the machine sky-high and off her right. Her coach and mum though are thoroughly impressed. (00:01:30)
Other mistake: In the study, Phyllis Reardon retorts bitterly at Magnum that he was kissing Ginger 'yesterday'. But they are staying at Robin's nest, and it's impossible that a whole afternoon and night went by without them talking about what happened - including Magnum to Higgins. And the doctor just came to give her a sedative for the shock...or an earlier day? (00:12:45)
Almost Home - S3-E10
Other mistake: When Magnum passes a can of nondescript soda to Bridget outside of the Navy building after the chat with Maggie, the vending machine has a big triangle of masking tape to conceal the Coca Cola logo for sponsorship reasons - however the production failed to cover the Sprite button which remains recognizable. (00:13:00)
Other mistake: The clock in the millionaire's limo has all hands (including the second hand) perfectly still. (00:02:00)
The Arrow That Is Not Aimed - S3-E13
Other mistake: Magnum mispronounces the word 'seppuku' calling it it 'seppuki', prompting Higgins to correct him. He plays the role of the usual Westerner who is unfamiliar with the word and concept. But in the previous season, in 2-9, "The Taking of Dick McWilliams", not only he already had to deal with the prospect of ritual suicide, but he spontaneously mentioned the word himself ("Seppuku? You're willing to let your daughter kill herself?") with the other person simply mentioning a vague 'honorable thing to do'.
Basket Case - S3-E14
Other mistake: During the game, Willie scores the 38-34 point according to the close-up of the electronic board, but in the wide angle when she actually shoots it, the score appears to be 30-31...from 30-30, which is odd, since it was a 2-point shot. (00:43:00)
Other mistake: Rick and TC are at the counter of the Chinese joint when they hear a bang and a car speeding off. The noises are almost simultaneous, which means the lone assailant exploded a gunshot from their car while they were at the wheel. Uncanny coordination, recovery time and reflexes, contrary to the parking custodian in a booth we see there, who reacts to the car passing by, but was unfazed and with their back turned after a shotgun has been supposedly been fired meters away from him. (00:28:25)
Other mistake: Marsha Mackenzie is supposed to be competent with certain aspects of men care; she comes from a wealthy family and she has been taking care of the men in her family all her life. And Magnum does show up at the Kamehameha club with a nicely done knot on his tie. When we actually see the actress tie that same not metaphorical knot though, it's very clumsy, crooked and differs in between shots (it's also done on an unbuttoned shirt).
Forty Years from Sand Island - S3-E17
Other mistake: Hank Palmer appears in the closing credits as "Hank Sorenso", but his last name is pronounced by everyone (and logically so) as "Sorenson", and Rick says his first name is Fred. (00:31:00 - 00:48:00)
Other mistake: The accountant first, then some minutes later the prince and princess arrive at the estate. They are bone dry despite the hurricane outside complete with pouring rain noises and strong winds. (00:05:35)
Other mistake: With power out Magnum somehow lights the gas stove with the knob, which is electric. Should have used a match. (00:26:40)
Other mistake: The killer is finally in action; they get a semiautomatic with a silencer from a case, then they do an ominous gun-in-hand walk bit (filmic stereotype where someone just walks with a gun out for no reason instead of concealing it). The shadow of the gun there though shows no sign of a silencer. The killer shoots indeed with a silencer - the audio implies that - but in the shadow you can see it is now a revolver. (00:44:20)
Other mistake: The Prince and Princess of Turbia are, according to Higgins, "Fixtures at Robin Masters' parties." Makes no sense then that they have no idea how Higgins looks like, since it's established that he's been taking care of the estate for over a decade - of course, Masters does not reside in Hawaii himself a lot, but earlier in the episode it is established that he runs those parties at his villa yearly.
