Episode #1.4 - S1-E4
Visible crew/equipment: When Lee is being interrogated, at one point (after the detective says "Are you crazy?") the detective walks towards the large two-way mirror and you can see a clear reflection of a cameraman in the lower part of the mirror. (00:27:31)
Other mistake: Throughout season 1: The emergency workers are sometimes seen wearing a black jacket with an English spelling mistake on it. It reads "FIRE EMS RESOUE." Obviously the last word should be "RESCUE."
Continuity mistake: At one point when Lee Byeong-chan is talking into a video camera the video camera battery level indicator shows 29%. When the view changes then switches back a few seconds later, it's at 22%.
Continuity mistake: When Park Eun-hee is talking into a video camera there are some on-screen icons for the camera: zoom, battery level, etc. Initially there are two guide lines on the zoom level bar. When the view changes then switches back a few seconds later, there is only one guide line.