Continuity mistake: Dwayne has his fingers on a different spot of the evidence bag with the ecstasy when the camera angle changes. (00:15:05)
Factual error: When JP shows the article from the Cowbridge Gazette, it is the Wednesday 22.01.16. January the 22nd was a Friday in 2016. Following article's date; Wednesday 2.2.2016. Actual 2.2.2016: a Tuesday. (00:15:25)
Continuity mistake: When Perrie Campbell says "Now I can see it", about the world out there, the bang on her right side is windblown. The wind is instantly absent in the next shot, just as in the rest of the shots from that angle. (00:16:35)
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)
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: 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: 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: 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)
Plot hole: Why would Sian let Griff into the shower room if she broke up with him the night before?
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: 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)
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)
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)
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)
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: 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)
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: 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)
Answer: Most likely they had only tropical exotic drinks, he wanted an old fashioned English beer.