The licence plate of Diana's car changes from a G plate to a J plate in the first five minutes of the film. Is seen again towards the end and changes from J when it is first seen again and then it changes back to G again.
Diana cuts her left arm with a wire cutter and blood is visible, but later in the bathroom she cleans blood off her right arm.
The conversation on the steps on Christmas Day was stated as 5pm. It would've been dark at that time in the UK, but the scene is in broad daylight.
When they are opening the military boxes of food, there are lobsters and other shellfish seen. The royal family is forbidden from eating shellfish. This is to avoid shellfish poisoning.
In the first dinning room scene when Diana breaks the pearls several pearls drop into her soup. Expensive pearls are individually knotted and if broken only one would have dropped.
The film shows a grouse shoot happening on Boxing Day. The grouse season runs from August 12 to December 10.
Bird calls in the film are of North American birds including red-winged blackbirds and Stellar's jays, as reported on This American Life episode 754 "Spark Bird" thisamericanlife.org/754/spark-bird.
At the start of the film Diana is driving to Sandringham and has got slightly lost and refers to a map while driving.
A shot from the passenger side of the car shows that the instrument dials (Speedo/Revcounter) are all stationary and at zero. This reveals that the car was not being driven, but is on a low loader, or in a green screen studio. The most likely reason for this is that it would have been safer for Kristen Stewart to play the scene without actually driving rather than have to act out the checking of the map while the car was driving down narrow country lanes.
The "British Armed Forces" in the beginning drive German left-hand drive DAF trucks and carry boxes with labeling of the German Army ("GWT" is an abbreviation of "Gewicht", meaning "weight", and the unit is the metric Kilogram).
When Diana is running away from the hunt with the two boys, she calls them 'slowpokes'. This is an American term and in England they would say 'slowcoach'.
Major Gregory goes into the estate grounds to invite Diana to get rid ready for dinner. It's 5 pm and she is sitting in sunlight, long after sunset in December.
Diana scratches her upper right arm with a wire cutter at 1.17.06 to 1.18.10 which drawing a little blood. But at 1.21.44 to 1.22.00, there is no scratch at all on her arm.
On the Boxing Day pheasant shoot there are a number of Land Rover defenders. One of which has an obvious 2016 plate (UK) and is especially obvious before the shooting begins, when Charles is drinking tea.
In the opening scene British Army soldiers are seen carrying the L85A2 (post-2009 model). This is 18 years too early.
When Diana is lost at Sandringham in her 1992 Porsche, the Land Rover that drives up has a 2016 number plate. Its tax disc appears to be correct for the period, but the number plate is from 19 years after Diana died.
The camera crew can be seen dollying in the rear view mirror, just before Diana gets out of the car and goes into The Duch Cafe.
Diana tells William: "The chef has made Souffle d'Abricots just for me". The correct name is "Soufflé aux abricots" or "Soufflé à l'abricot".
When Diana is driving to Sandringham she is wearing Chanel sunglasses. Princess Diana never wore Chanel because the intertwined C's reminded her of Charles and Camilla.