Corrected entry: Filming stopped every day at noon because the heat reched temperatures of over 130 degrees F.
Corrected entry: Several times, when Poirot explains that someone could have been the murderer, we see scenes in which someone is peeking through the window and observes when Jackie "shoots" Simon in the leg. The distance between Jackie and Simon varies frequently. It's particularly apparent when Salome Otterbourne "peeks" through the window, when Jackie and Simon are almost at arm's length, vs. the first time (when it really happens), when they are maybe a couch length away from each other.
Correction: The scenes each unfold with subtle differences because they aren't of the actual event, but rather Poirot's version at that time.
There is technically no reason why the premise of the murder (aka how Simon gets shot) and all the ancillary details would vary in Poirot's story. Sure, it's not 'the actual event' but the version has to be believable and can only be a variation of what we originally saw (and Poirot didn't). For instance, when he accuses the doctor to pocket the gun, the moment when Ferguson is 'distracted' is identical but Simon's shirt collar is in a completely different position. Or when the doctor calls Ferguson a "Stutzer" telling Miss Ottenbourne to come along, the delivery of the line is subtly different. If everything were *completely* different and just Poirot's mental construction without visual connections at all to the actual scene he after all did not witness, fine, but here we talk about small differences between alternate takes of parts of story unaltered by Poirot's theories.
Correction: You can see by the almost complete absence of shadows in some scenes (in particular, the Karnak Temple scene) that some scenes were shot at and around noon.