Audio problem: When Dre is leaving Meiying's violin practice in the auditorium there is a long shot of her playing her violin showing her left side as Dre walks to the exit. The notes she is playing are vibrato - varying the pitch of the notes by rapidly pivoting the finger on the strings - but her hand is perfectly still. Even though you can only see part of her hand it is obviously that her playing style doesn't match the notes being played.
Audio problem: At one point in the film the television in Dre's apartment shows a screening of the Spongebob Squarepants episode "Mermaidman & Barnacleboy III", but the Japanese dub is actually from the episode "Sailormouth" (notable by the dolphin sound effects).
Chosen answer: 1. It was unexpected. In China, not clapping is considered a compliment. 2. They feel Dre is a distraction. 3. Yes. There are martial arts tournaments in China as depicted in the film. 4. Yes. The scenes which feature the Forbidden City, Wudang Mountain, and the Great Wall were filmed on location.
MasterOfAll