Other mistake: In the song "A Rumor in St. Petersburg," according to the closed captioning, the characters sing the words "no proof of fact." According to the lyrics in the soundtrack booklet, they are actually singing "or through a crack." And if you listen, it's actually what they are saying.
Other mistake: The calendar next to Mima's bed has the number seven displayed at the top, indicating that it is the seventh month of the year, which is July. But there are thirty days shown on the calendar page, when there are 31 days in July. (00:52:36)