When the group enters the castle from the rainstorm, they are perfectly dry.
When Death tries to restore the ruined positions of the chess pieces, it is seen that the king has been damaged, but in the following, last move the king is whole again.
In a close shot at the seashore, the sun is visible behind Block's back, but it's gone in the following wide shot.
When Death is putting the chess pieces back in their correct places after they have fallen, Antonius has three chess pieces in his hands. In the following shot, he is holding his sword.
In the influential scene with Block playing chess with Death, the chess pieces are incorrectly repositioned after they are knocked over.
During the game of chess played against Death, the table appears incorrectly rotated. According to the rules of chess, the upper right square of a chessboard shall always be black (and not white as seen in the movie). Death and Antonius should know better than to make this mistake.
At the seashore, Block's face is brightly lit from the side, yet the rising (or setting) sun is behind his back.
When Raval steals a bracelet off a dead woman's wrist, her hand slightly twitches.
The chess players focus on capturing the Queen. The Queen was not a super-powerful piece until centuries later when a recent chess-variant initially called "chess of the mad queen" became more popular than the classic game.
In the witches' forest, you can see the windows of apartment buildings between the trees.
The knight and his squire return from the Crusades, to find their homeland suffering a Black Plague pandemic. The last Crusade ended in 1291, and the Black Plague didn't reach Europe till 1347, more than fifty years later.
When Lisa (the Blacksmith's wife) is with Skat and laughs, her inlays are visible.
Just before the arrival of the Christian entourage, Jof and Mia were performing their presentation at the village. At that moment, both of them were supposed to slowly stop playing their instruments - Jof, who was playing the stringed instrument and Mia, playing the tambour. The sound of the stringed instrument can be heard as Jof is not stroking the strings anymore.
Jof's hand movements on the lyre do not match the audible notes.
When Skat and the blacksmith reunite with the group, a forest backdrop is visible in the background.