The Royal We - S3-E2
Revealing mistake: On the RV of the guy being accused of molesting the girls, someone has written "PERVERT" in red spray paint. At a point you see Lightman next to a car, and the RV in the background, and the text is mirrored reading: "TREVREP", showing that during editing, this shot was flipped. (00:15:30)
Revealing mistake: The dead victim is being examined in the morgue, right as the mortician says "the kid put up a fight" the dead victim swallows as she strokes his hair and says the word "fight." (00:09:35)