Other mistake: Considering who the culprit is and the fact that they were speaking to the victim at a distance just before shooting them, it's impossible for Charity to make it back to the party before Stephanie. While they could have run faster, it makes no sense for them to casually appear to the left area; they should either come from the right - the direction where the shots were fired - or we are supposed to believe they circled around passing behind the burning warehouse. Furthermore, the film's ending reveals that the murder was not premeditated, so Linda was not actively helping.
Other mistake: During the scene in the small square of Capri, extras are casually recycled between different shots. For example, early in the scene, when Anna Kendrick stands in front of her stalker, the same couple (he's wearing a blue T-shirt, she has a shoulder beach bag and a denim jacket) repeatedly walks behind her from right to left and even enters the bar in the reverse shot when Irene rolls her eyes, admitting her guilt. (00:52:00)
Other mistake: Stephanie confronts her stalker in the small square of Capri; the iconic clock tower shows 9 a.m., but shortly after, when Irene shows her the phone, it reads 12:22. (00:52:00)
Other mistake: Sean's room got flooded after the murder, but it's unclear how. The shower had a drain against the wall - far from where the body or glass shards could have blocked it. When falling, the victim didn't knock over the 'phone,' which continued to pour water only inside the shower. Later shots of the room make the flooding even more confusing; the killer leaves through a standard single door, but when the body is discovered, the bathroom opens into the living room with a double door. (00:47:00)
