Continuity mistake: The guests are coming up the ladder leading them to the Karnak. The French maid bows slightly to the moustached staff member and walks past him, only to repeat the gesture in the next shot. (00:35:00)
Continuity mistake: In the first scene on the boat, Simon uncorks the bottle nearly giving his wife a heart attack. In the background he's holding the magnum bottle with just one hand, in the next one he's using both. (00:35:30)
Factual error: A .22 shot would be 120-140 dB, muffled with a pillow down to 100-120 dB. Only one person heard the second shot? No one heard the third? Plus at the end there's no way a .22 could pass through a male chest cavity, and halfway into a female chest cavity - it's too low power.
Plot hole: This adaptation further exacerbates the problem of previous movie and TV versions; in the novel, Jackie would make the female designated witness talk over and over pretending also to get drunk after Linnet left to go to bed. In the Ustinov version it happened too, but the diversion didn't seem to last more than a couple minutes. Same in the Suchet version. Here, Simon even provokes Jackie practically the moment his wife exits the room. There's no time whatsoever for her to change and get in bed, let alone fall asleep.
Other mistake: Poirot saves his entire company except his captain - that's what it was stated, although it's unclear how that can be the case since the explosion was massive and left Poirot disfigured and had several other companions close. That's besides the point though, which is; the captain walked into a trip-wire across the bridge, but earlier shots showed the Germans (several of which were waiting on the same side the Belgians come from) retreating in haste, running exactly where the captain walked. The trap would work only if the Germans were waiting on the other side of the river. There was no chance for them to arm the trap during their hasty escape.
Other mistake: In the origin story of Poirot's facial hair, we see the damage on his cheek is massive, well into the cheekbone. His girlfriend says he'll grow a moustache to cover it, and surprisingly, it works - nevermind the fact that scar tissue wouldn't grow hair. When we see the scar without the moustache, while smaller than the initial damage, it still extends into the cheek at the level of the nostrils in a way that the 'stache couldn't seamlessly cover like in the rest of the movie and its prequel.
Factual error: The movie takes place in 1937: the new and improved Salome Otterbourne of this version has a repertoire of blues songs that are a few years posterior to that date, many years if we count the Rosetta Tharpe versions actually used in the movie. An argument can be made that they are all 'live performances' from a fictional character regardless of the vocalist who actually performed, and so the only song truly 'impossible' in 1937 would be "Shout sister shout", written in 1941, but we don't actually see Salome sing it. She does perform "Up Above My Head" and no recorded version of it exist before 1941, but it comes from a traditional gospel song.
