Factual error: Emer Byrne's Irish passport is fake. Look at the expiration date; the day of that date does not match the date of issue. A passport issued on September 24 wouldn't expire on September 01 as seen there, but on September 23. (00:16:15)
Other mistake: The police force is searching the room of the deceased at the beginning of their investigation, Humphrey stands in front of a map of Saint Marie with the exclusion zones. The map though shows an island upside down compared to the map you could see in Episode 7 of season 2. (00:10:10)
Factual error: When Humphrey makes the big reveal opening the suitcase full of cash, it's a bunch of wad of bills, each with the currency straps indicating a value of 50,000 (Eastern Caribbean) dollars. Thing is, it's all in $50 notes, which means there should be 1,000 bills in each wad, which is obviously not the case. (00:47:20)
Continuity mistake: At the end of the episode Commissioner Selwyn Patterson warns Dwayne against equating him to farmyard animals. His hat switches hands during the scene, as you can see when he turns around to leave, and his left arm is down his side instead of bouncing the hat as shown in the next shot. (00:49:50)
Continuity mistake: During the denouement, in the close-ups of Mayor Joseph Richards he and especially JP in the background have strongly sunlit areas over their bodies. In the wider angles, the set is uniformly in shadows. (00:46:30)
Continuity mistake: When Richard has the epiphany about the case with the realization about the mayor, he keeps looking left and right and babbling with both markers in hand. The white one though in some shots has its red lid on, and in others hasn't. (00:32:00)
Continuity mistake: The whole sequence with Humphrey doing his 'visually aided' re-enactment of the night of the murder contains little shot-to-shot inconsistencies from the moment he takes the second whiteboard on. The photo switches hand, he leans to the top of the board when it's time to stick the picture on it, but the same hand is lower on the board at the cut, and so on; in some shots he's touching the board and in their reverse angles he is not. (00:35:40)
Revealing mistake: When Dwayne holds the copy of the local newspaper with his goat comment making the headline, the text of the article repeats itself; you can see aligned in both columns the name of the commissioner accompanied by "pictured right." (00:23:15)
Continuity mistake: Martha and Florence are chatting in front of two glasses of wine, courtesy of Catherine. Martha's hand is at a different height, higher on the stem of the glass in one angle, lower against its base in the other main angle the scene is shot under. (00:20:35)
Audio problem: Catherine has been a character on the show from season 1, almost the first episode. Never has she pronounced the name of the island, Saint Marie, like she does in this episode: "Welcome to St. Mary." (00:20:20)
Continuity mistake: Florence and Humphrey take a walk with Emer Byrne. Behind them, a man with a rather noticeable orange T-shirt. Later in the scene when they go back to the jeep, the same man appears again together with the other guy he was chatting with, again walking back and forth just to pad the background. (00:16:00)
Continuity mistake: When Humphrey points out of the strangely lacking item amongst those lined up, the items in question change position between shots; when there's the shot of the whole row, the canteen is at an angle, it is parallel to the rest when the camera pans in close-up. The sandwich bag too is folded differently. (00:06:00)
Factual error: The stratagem used to conceal the murder and disguise it as suicide is absurd from the start; it relies on the old trope of a gun "silenced" shooting through a pillow. It simply does not work, a gunshot in the early morning in the empty camp would have not been dulled down significantly by a pillow, and still be heard.
Plot hole: The shower room door has a lock, that as shown in the denouement the killer never closed - making it fairly obvious that the victim did not lock herself inside the room to kill herself. Another minor but still significant problem with the stratagem used; the killer shot the girl in the chest; even if they didn't do any gunshot residual test on her hand, the trajectory of the bullet still would have proven the impossibility of a suicide.
Continuity mistake: DI Goodman is inspecting the pillows; when he gets to the second bunk bed, you can see that handling the pillow he accidentally catches with his arm a blue piece of clothing placed on the railing, dragging it a little along the way, towards the vertical support bar. The next shot is evidently from a previous take, because that blue rag is in the initial position, away from the bar. (00:39:10)
Continuity mistake: When Goodman sprints away from the banquet, the cue cards in Dwayne's hand move from both hands to a lowered left hand in the faraway shot. (00:38:40)
Continuity mistake: When Goodman jumps up yelling "yee-haaw!" messing the wedding table, Commissioner Patterson grabs a towel with his left, but at the cut he is using the right hand to clean his left. Likewise, Florence has in the second shot a hand on her chest, but she didn't have that pose already in the previous, it was just her initial reaction. (00:38:00)
Continuity mistake: Humphrey gets next to Leo's bed saying "Hey sexy." He has a hand in his pants and the other on the phone, but they swap place at the first cut. When he gets up and protests that he loved Sian, the phone disappears. (00:39:10)
Continuity mistake: After hearing about the theory that perhaps Sian and her knew each other from back home, Perrie Campbell walks away. Goodman grabs the manuscript from the table, but his arm does not move in the reverse shots. He then puts it back, but when it is his turn to stand up, it is nowhere to be seen - yet it didn't look like he could have put it back much far away. (00:16:55)
Answer: Most likely they had only tropical exotic drinks, he wanted an old fashioned English beer.