After Dani witnesses the copulation of Christian and Maja, she vomits as she runs out of the archive building. When Christian runs out of the archive building, the vomit has gone or already dried even though it has only been a few minutes.
When the cremation of the two elders is finished, nothing is left of them but ash. Even a large fire like the one they were burned over would not be hot enough to reduce them all the way down to ash. There should still be many large chunks of bone left.
When Simon is found in the barn, his lungs have been pulled through his back, but he is still alive and breathing. The lungs are inflated and deflated by the diaphragm and the muscles in the trunk; once they were pulled out, he would immediately suffocate.
Scattered throughout the fields, saplings can be seen with pink blossoms on them, presumably young fruit trees. Because this movie is supposed to take place in the middle of summer, the trees should not be blossoming, but fully leafed out. Fruit trees only bloom in early spring.
Hälsingland is more of a cultural region in Sweden and has no administrative significance. Therefore, there are no Hälsingland road signs in Sweden like the one that can be seen during the car ride to Hårga. The correct name on the road sign and the county would be Gävleborgs län (Gävleborg county).
The festival portrayed in the film is meant to be a Summer Solstice event yet involves a 'May Queen'. The European summer solstice is in late June, and a May Queen is usually crowned on the 1st of May- the first day of Summer.
The villagers don't wear authentic Swedish folk costumes because the Hårga are an isolated cult with their own traditions and folklore. The costume design incorporates elements from several cultures using Romanian, Hungarian and Swedish materials embroidered with runes.
In the closeups in the closing scene, it is obvious that the floral May Queen dress and headwear worn by Dani are made of artificial flowers with cloth petals and plastic stems.
When Dani sees grass growing out of her hand, her fingers are oddly chubby and discolored, indicating that her hand is either a prosthetic or poorly done CGI. Upon closer inspection, it's clearly Pugh's hand from a low angle in different lighting than the rest of her body. CGI grass or not, it's clearly her own hand.
The sun is referred to in terms as "father", but in Scandinavian cultures the sun is often referred to as feminine because the Norse word for sun is a feminine gendered noun. For example, in Norse mythology the Sun is said the be dragged through the sky in a chariot by a goddess.
For the whole mating ritual thing they do, the whole purpose is to have the highest success in pregnancy, but if the girl just had her period the other day (to put the blood in the drink) then she wouldn't be ovulating yet. So the chances of pregnancy wouldn't be that high.
While the visual transition is well done cinematically, the inside of an airplane's lavatory door looks much different than depicted in the plane. Additionally, the "lock" sign is pointing in the wrong direction, the coat hook is upside down, and there is no door handle to open the door from the inside, just a pull mechanism to close the door. But this is not a bi-fold door, so that would not work and Dani would be stuck in the lavatory.
The historicity of the blood eagle is still a discussed topic, whether it has actually ever been done, or whether it is just later misinterpretation or purposeful demonizing of pagans by Christian authors. In any case it was a torture method used in vengeance, not as a part of summertime celebrations.
The Americans react to the sun being up late at night. The sun doesn't set until after 10:30 PM in the area around midsummer, but the lack of long shadows reveals that the scene does not take place in the late evening at 61° North (where the story takes place) but rather around noon at 47° North (Hungary, where the supposed Swedish scenes are actually filmed).
The firemen responding to Dani's parents house are not wearing their breathing masks. With there clearly being enough CO to have killed everyone in the house, they would quickly be overcome themselves.