The Ferrari sticker on Russell crowe's Lambetta moves locations.
Towards the end of the movie, when Father Amorth and Father Esquibal meet the Pope, the latter's ear is intact, without so much as scarring lines where he had been bitten by the boy, earlier.
During the first exorcism the afflicted goes from being bound with ropes on both wrist to unbound back to being bound.
The movie starts in a village in Italy, then in Rome and in Castille, Spain (where I am from). When construction workers speak, before they get burnt, the one who speaks does not have a Spanish accent from Spain. Then, when they take the boy to the hospital, the doctor and the interpreter do speak in Castilian Spanish, but in the subtitles in English they say they are speaking in Italian.
Father Amorth, the Pope's exorcist, does not actually use the Catholic rite of Exorcism when performing exorcisms.
When introduced to the American family that moves to Spain, the aerial shots, both for the proximity to the sea, its cliffs, and the green mountains, seem to belong more to the northern coast of the country rather than to the central and inland area of Castile.
A monseigneur would have known that it is the Book of Revelation, not Revelations.
At 51:08 when the scooter is tied tot the well you can see the knot unraveling as Gabriel puts force on it.
The movie is set in 1987, yet a Swiss highway toll sticker from 2021 is visible on the windshield of Julia's car.
There is no mention of the Iron Maiden device prior to the 19th century. Additionally, there is no evidence that it was ever used by the Inquisition and may, in all probability, have been a myth fabricated to sell tickets at a tourist attraction.
In one scene at the cave it is shown a map of the time of the previous exorcism there and the characters talk about the year 1475. The map shows the Americas, which were discovered in 1492.
In the movie, Father Amorth rides an elderly Lambretta motor scooter all the way from Rome to a location implicitly near Burgos in northern Spain: a journey of almost 1,200 miles. This is an absurd distance for a vehicle capable of - at most - 60mph for short bursts. Had he somehow managed to average 40mph on that journey, and ridden non-stop, that still represents over 30 hours of riding. Yet he dismounts the scooter and proceeds immediately to the work of exorcism.
In the library, both Father Amorth and later the Pope translate the note "Peccata tua inveniente te" as "Our sins will seek us out" but "tua" means "your" and "te" means "you".