When the main characters meet Aslan on the sandbank, Aslan's shadow changes from being toward the other characters, to away from them, and back again between shots.
When Edmund and Caspian are looking out the prison cell watching the sacrifice being made in the harbor, the "Dawn Treader" is not to be seen in the harbor.
When Lucy places the sixth sword on Aslan's table, there are twigs scattered around and under the swords, but the next shot shows all six swords lying in a clear spot on the table with hardly any twigs.
At Aslan's Table, Lilliandil's arms suddenly change position.
Caspian hands Edmund the torch he had left behind three (Narnian) years earlier and it still works (as shown by Edmund's using it to confuse the sea-serpent in the Island of Darkness fight). Even using the book's one year passing in England, the zinc-carbon batteries in the torch would have been discharged long prior, and also leaked (spoiling the entire torch). Alkaline dry batteries (which could possibly last that long, as inferred from a commercial for the Duracell brand) were not commercially available until the 1950s (the patent for these was filed 1957/10/09, and granted in 1960).
In The Chronicles of Narnia: Prince Caspian (2008), Caspian (Ben Barnes) spoke with a pronounced Spanish accent, as did the other Telmarines. In this film, Caspian now speaks with an English accent. This is done purposefully by the filmmakers, who no longer needed to match Caspian's accent to the other Telmarines, so they chose to use the actor's more realistic natural British accent. People's accents change over time in real life as well.
Given the passage of time in Narnia is faster, Prince Caspian would be long since dead by the time the children make their arrival.
This is addressed in the books, as time passes differently, sometimes less fast than other times.
This is addressed in the books, as time passes differently, sometimes less fast than other times.
When Eustace falls into the valley with the dragon's hoard, the ground at the top and bottom of the cliff moves as he falls on it.
As the Dragon is pulling the Dawn Treader with his tail, his shadow does not match up with his flapping wings.
Edmund's bicycle has modern cable brakes. In the 1940s British bicycles would have used rod brakes instead.
When Susan is writing Lucy and Edmund a letter, the camera pans to a high quality, color photograph of the four siblings in uniforms. Color photography was only rarely used by professionals even 5 years after WWII ended and would never have matched the modern clarity of the prop photo.
King Caspian introduces Edmund as High King. Peter is the High King of Narnia, not Edmund. The title does not pass on.
When dragon Eustace gets stabbed by the sword, he gets stabbed on the left side of his body. When he turns into a boy again, he touches the right side of his body as if the sword hit him there.