Continuity mistake: When Maria leaves the Abbey to go to the Von Trapps, she walks for a ways, then takes what appears to be a rather long bus ride. This shows a fair amount of distance between the Von Trapps' house and the Abbey. Yet, when Maria snuck out to return to the Abbey during the party, it was night, and she had no ride waiting. Later, after the Captain tells the children he will marry the Baroness, they walk to and from the Abbey in an unsuccessful attempt to see Maria, and in an apparently short amount of time. From the initial bus ride, the Abbey was simply too far away for those walks to be believable.
Continuity mistake: When the children and Baroness Schrader are playing the game with the ball, they all have numbers which they say as they bounce the ball to one another. These numbers then change once they start throwing the ball (Friedrich starts as 4 and becomes 5, the Baroness starts as 5 and becomes 6, etc.).