After the thieves capture Christina, they gag her with a cloth tied over her mouth and around the hood of her cloak. When Christina is tossed into the back of the thieves' wagon, her gag is no longer tied around hood, which now lays down around the girl's shoulders.
When Buster is practicing the accordion after Chauncey has left to find Christina, he is not wearing his brown jacket over his green shirt. When he opens the package Chauncey left for him, in the closeup of him holding the note, his sleeve is brown like that of his jacket.
At the beginning of Christina's song "Things That I've Collected", she pulls a heart-shaped-stone a button tied on a string and a doll out of her bag, placing them on a shelf. When the camera pans back into the room after the fantasy sequence of Christina in the sky, there are now two heart-shaped stones on the shelf and the button and string are nowhere to be seen.
Austria didn't have a queen in 1818, as suggested in the movie. Austria was ruled by Emperors and Empresses, in the time of the movie's setting it was Emperor Franz I and his wife, Empress Karoline Auguste von Bavaria.
Queen Therese IV aka Therese von Saxony-Hildburghausen was never a queen of Austria, she was the queen of Bavaria and it happened 7 years after the movie's setting. After marrying Prince Ludwig I she only became queen of Bavaria in 1825.
Oberndorf didn't have a mayor in 1818 as it was not considered a town. The first official mayor Mathias Hager was elected only in 1927.