Plot hole: The whole premise of the plot is that nobody is staying at End House but Nick (and the servants); she even says explicitly that there is just one room that is usable and everyone else stays at the Majestic. During the party though, Freddie tells Maggie to go get her coat which is "in my room." They are at End House, not the hotel, how would Maggie have a room there? (00:35:00)
Plot hole: The killer's plan needs to have Maggie at End House - but it's achieved through Poirot's proposal to have Nick call her to act as added protection. But this makes no sense; Maggie's presence would have not protected Nick in any of the alleged attempts to her life; the frame would have crushed her too, she would have died in the car, she couldn't have prevented the rock from falling, and Nick was shot while the most famous detective was with her, even! A random little girl from Yorkshire would have not mattered, so it makes no sense that Poirot endangered someone for no gain.
Factual error: Poirot has just suffered "a turned ankle", in his words; he's talking with Hastings and the kind woman who helped him out, when their conversation gets perturbed by the noise of a plane. Which is surprising, since the plane in question is a Volmer VJ .22 Sportsman, a plane from the 50s, way after the 1930s setting of the episodes. (00:06:40)
