When Cynthia and Thomas are lost in the woods she lies down to sleep and she has his jacket over one shoulder. He reaches down and pulls the jacket all the way over her. They cut to him and then back to her and the jacket is still only over one shoulder.
When Nils (Lauritz Melchior) sings "Vive la compagnie" he pronounces it "com-pa-NEE" but the word is actually pronounced "com-pa-NYEE".
The balconies at the hotel are obviously a set since there is no glass in the windows or doors. This can be clearly seen since there are no reflections when the characters move past them.