After McGarrett waits for Charlie Hazard on the beach, he receives a radio call that Charlie has been found shot. McGarrett is wearing a dark blue suit - about as dark as the tie he's wearing. Although he tells the dispatcher that he's on his way, when McGarrett arrives at the scene of the shooting, he's wearing a noticeably lighter blue suit, especially compared to his tie.
The view through the rifle's scope does not have cross hairs. Without cross hairs, it would be impossible to actually aim the rifle.
McGarrett gets a phone call in a motel room from Johnny to play a record on the record machine there. One can see that McGarrett starts the record at the beginning and the song plays for about one minute and then ends. Then McGarrett is seen removing the needle and the position is at the end of the record. On the large 33 1/3 record the music would play much longer than the approximate one minute.
That record isn't a 33, it's a 78. Much older technology. Not an Long Playing (LP). This is not an egregious error. As it turns at 78 RPM, it takes over twice the surface area to hold a song as a 33 1/3 RPM recording.
When Johnny Kling (Rich Little) gets Thayler (Don Knight) to the top of the fuel tank, Thayler can be heard saying "No, Johnny, no!" but his mouth does not move as he says this.