Episode #1.7 - S1-E7
Continuity mistake: When Kang-bae, Weol-ju and Guibanjang are talking in the staff room, Weol-ju tells Kang-bae to practice some more. Weol-ju has a pretzel in her right hand when she says this, but when the shot cuts to Kang-bae, the pretzel in Weol-ju's hand has disappeared. (00:38:40)