Episode #1.7 - S1-E7
Continuity mistake: When Kang-bae leaves the staff room to go practice, the sandwich that Guibanjang is holding has one bite taken out of it. Then it cuts to a shot of Guibanjang saying "Win first place", where there are now two bites taken out of the sandwich. Then part of the sandwich reappears again in the following shot. (00:38:44)