When the agent in the alley takes his cyanide pill and kills himself, Diana and Steve seem oblivious to the fact that there are 5 other agents still alive and unconscious in the alley, that they could get information from. They simply walk away, leaving the information these agents have undiscovered, and a bunch of German agents in the alleyway to go on their merry way once they wake up.
Steve Trevor spots a motorcycle to make a getaway on. The bike shown is a period-correct machine, probably a Douglas or a Triumph, with a drive belt made from leather links. The scene cuts to him riding through a forest on a much faster, much more modern machine with telescopic suspension forks - which weren't invented until 1935 by BMW for the R12.
When the party lands in Belgium, one can see a river boat named after Édith Piaf, who was only 3 years old and had not started her singing career.
When Steve gets dressed after his bath, we hear the sound of a zip. During WWI the zipper was a new invention and only being used in American uniforms, not in other nations uniforms or civilian clothes, and Steve is an American serving in British intelligence.
When Diana is racing away from the gala on a horse back to the village, the blue dress she was wearing flies off, leaving her in her Wonder Woman costume. However, if she had been wearing her costume under the dress at the gala, it would've easily been seen peeking out the top of the dress, since the dress is much lower cut across her chest than her costume is.
When Steve is telling the Amazons about the Germans having Turks build bombs for them, the facility shown has two Ottoman flags that feature a white crescent moon and a white star on red. Those flags belong to present-day Turkey. The Ottoman/Turkish flag used between 1844 and 1936 was very similar, but had a visibly thicker moon and a plumper star on it. Since the movie is set in 1918, the Ottoman Empire would still be using that flag.
The song sung by Charlie in the village cafe, "I'll Walk Beside You," was written in 1939.
In the credits, the word "Cavalry" (horse-bound soldiers) is spelled "Calvary" (Latin word for skull, name of the hill of crucifixions). Big difference in meaning, but a common spelling error.
While the song that plays in the cafe in Belgium ("Sous Les Ponts De Paris" or "Under the Bridges of Paris") was written in 1913 and therefore period-appropriate for WWI, the recording is by French singer Lucienne Delyle, who was born in 1913 and didn't record the song until 1950.
The film repeats the common thought that British General officers stayed far behind the lines and were callous regarding the deaths of their men. In fact 78 British Generals were killed in action in World War I. British Generals above Division command did stay behind the lines.
By November 1918, the war had become very mobile, and while elaborate fixed defenses still existed, "No Man's Land" was still a shell-blasted wilderness; the Allied troops' greatest problem was dealing with the Germans who dug new trenches every evening.
In the initial battle with the Germans on the beach all of the Amazons are on top of a cliff, from which they are easily able to reach and kill many Germans who are still in their boats. Yet they give up the high ground from which they can safely and easily pick off the Germans. They then engage in hand to hand combat on the ground with enemies who clearly have superior weapons. For a group of warriors who have spent their whole lives training and fighting they would know that giving up their strategic advantage would be foolish and put many of their lives at risk. It could be reasoned that they gave up the high ground because Diana was down on the beach, alone with a stranger. They knew Diana's secret and protecting her would have been their priority, not their own safety.
The railway carriage (US "railroad car") at the port in 1918 is named "Southern Railway". The Southern Railway did not come into existence until 1 January 1923.
Diana has no idea what a secretary is, among a few other terms, despite the fact that she is fluent in hundreds of languages, including English.
The movie takes many liberties with Erich Ludendorff's biography, from murdering his superiors with chemical weapons to his death date. However these are deliberate products of a plot that diverges significantly from real-life history in many other respects. They are not goofs.
In the final battle, when Diana is fighting Ares, there is a Mark V Tank, and then later one is picked up by Diana. The Mark V is a British design and is unusual to be found in a German staging area. However, this is military research facility and it is quite possible that the Germans have captured British tanks for research purposes and developing more effective weapons against it.
At the airfield in the final battle, the background shows 3rd generation hardened aircraft shelters, a 1980s design.
After liberating the town of Veld, Diana and Steve are seated in the town square with mugs of beer. Diana has a beer in her left hand and sets it on the fountain. When Steve stands to ask her to dance, she is holding the beer in her right hand and sets it down again.
All the building signs at the German airbase where the mustard gas is loaded into the bomber are in French, and so is the writing on the blackboard inside the command tower/office where Diana and Ludendorff fight. This makes sense given the geographical location of the base, namely Belgium where all military writings at this time were still in French instead of the Flemish (Dutch) spoken by many of the soldiers.
When Steve runs after Diana as she flees from the gala, he is not wearing his hat. When he emerges from the building, he is wearing it.
During the gala, the main characters and guests dance but there is no ballroom music. There is a musical cue to support the scene's emotional tone, but the ballroom itself is nearly silent.
When Diana and Steve are sailing to London, they both fall asleep near Turkey (where Steve's plane was shot down) and wake up, seemingly the next morning, in London. Not only would an un-helmed sailboat almost immediately drift off course, a sailboat trip from the Eastern Mediterranean to London would take several weeks. [Arriving in London, Steve says "We caught a ride." The boat is tied to a steamer and is being towed. There is no reference in the movie as to the location of the Amazon Island. In the comics it is in the Atlantic.]
There's an obvious man dressed as an Amazon by Antiope when the Amazons charge on the beach during the battle against the Germans.
There is no explanation as to how Diana learned to deflect bullets with such expertise, as guns seemed to be unknown to the Themyscirans until the Germans showed up on their doorstep. If she learned this skill from Antiope, then why didn't Antiope, the best warrior on the island, simply deflect the bullet that killed her? She clearly saw it coming.
When the Germans attack Themyscira early in the film, they are in small boats launched from a larger boat, maybe a cruiser or destroyer, that has penetrated the island's protection. As the Germans and Amazons fight, the larger ship is shown to be listing further and further, to the point of capsizing. This would explain why it is never seen again.
As Hippolyta leads the Amazons onto the beach, they briefly pause and the person just behind her is clearly a man in female armor.
When Diana is using an iPad and typing on a BlueTooth keyboard, a virtual keyboard is visible on the screen. In reality, when such a keyboard is connected, the virtual keyboard is automatically hidden.
In the climatic battle when Ares escapes from the Lasso of Hestia and throws Diana away with a blast, she falls on the ground with the lasso folded and fastened on her belt.
The aeroplane in which Steve Trevor escapes from Ludendorff's base is white when he steals it in the flashback, but red in his first scene when he crashed it into the ocean off of Themyscira.
Throughout the movie, Diana's wristbands appear/disappear without any explanation.
When Diana and Steve are having a meeting with the generals and it is discovered Diana can read Dr. Poison's book of formulas, there is a shot where Diana is missing a button on her overcoat. In the very next shot, it is back on but askew, and in the shot after that it is back in alignment with the other buttons.
While standing outside Cafe Buvette, Diana and Steve go from no cold breath to cold breath (where it looks like steam), to no cold breath again.
After walking through the mud, Diana's boots are spotless.
During the trench scene, there's a woman talking to Diana explaining what happened to the village where she lived. She speaks in German, however Diana answers her in Flemish.
During the battle scenes, Diana's hair goes from messy to perfectly curly and neat. This occurs multiple times during fight scenes.
When Diana is dancing at the gala with the sword in the back of her blue dress, the hilt of the fake sword leans far to the right when Steve is with her, showing that there is no sword at all, just the hilt.
Diana took off her black cloak at No Man's Land right before she emerged from the trenches. Much later, after the fight in the village of Veld, she is wearing her black cloak when the old man takes a photograph of all our heroes. Did someone really go back to No Man's Land to collect her cloak?
The village of Veld is allegedly a French village (the name of the town Hazebrouck is on the map and information on buildings are all in French). However on the awning of the bar, there is the word "bier" which is in Flemish or German. In French, it should be "bière". However, this might be correct, as Hazebrouck is in French-Flanders, where a lot of people used a dialect of Flemish at that time.
During the trench scene where Diana is arguing with Steve about rescuing the citizens of Veld, there is a soldier on the ladder behind her (looking across No Man's Land). The shot momentarily changes to Steve and back to Diana, at which point the soldier vanishes.
Briefly during the first London rail terminus scene, overhead wire gantries can be seen in the background of a type that were not in use until the 1950s on-wards.
When the crowd is cheering the armistice in the streets of London, one assistant is carrying a portrait of Kaiser Wilhelm II. As the German monarch, it makes little sense that anyone would be holding his portrait at a British celebration of his defeat.
During the gala, Steve's not wearing a hat. He wears one when leaving the castle for about ten seconds and goes to the forest with Diana with it missing for the rest of the film.
It was daylight and not snowing when the old man took a photograph of the heroes after the battle in Veld but the photo Bruce Wayne sends to Diana shows snow falling.
The movie starts, in Paris, in the morning as Diana goes to her office in the Louvre Museum. Upon looking at the photo sent to her by Bruce Wayne, her flashback memories ensue (i.e., the entire movie). When the flashback ends, it is now nighttime outside with her on the rooftop in her Wonder Woman outfit. This suggests that she spent the entire day thinking about all that happened 100 years ago. Even if she wool-gathered on the job, it shouldn't have taken all day.
World War I ended in 1918. Diana was perhaps 20 at the time. She later worked at the Louvre, some time after the pyramid was built in 1989. That's over 70 years, making her at least 90 when she worked there. She looks pretty good for a nonagenarian. (She obviously aged while on the island.)
Diana Prince is an immortal Amazon princess and thus would not be subject to the normal rigors of aging. The time frame of her childhood and upbringing are deliberately obscure. She may be hundreds of years old at the time of these events.
When Diana is taping the email thanking Bruce Wayne for retrieving her old photo, she types "Thanks for bringing HIM back" but in Issue, she typed "Photograph". Although maybe she was talking about Steve Trevor, Wayne didn't know she was romantically involved with Trevor.
The license plate of the Wayne Enterprises armored van "JL-828-VZM" (shown in the Paris located opening sequence) is wrong. In the current French license plates format, there are only two characters in the last group.
Diana at age 8 speaks in a Scottish accent which changes to an English accent to almost no accent to a "Themysciran" accent.
In Batman v Superman: Dawn of Justice, in the photo of Diana and the team, she is seen wearing her shoulder strap on her right side. However, in this movie, when the photo is taken, she is wearing it on her left side.
At the airfield in the final battle the background shows 3rd generation (1980s) hardened aircraft shelters.
At one point a map is shown. They locate the 'fictitious' village of Veld near the city of Hazebrouck. That's a city in the North Of France. So, not Belgium as the plot suggests. Then you hear some locals comment on Wonder Woman's destruction of the church tower. They do it in Flemish, but not with a West-Flemish accent (as spoken by some at the time in Hazebrouck).