The Glove That Rocks the Cradle - S7-E16
Continuity mistake: At the very end of the episode, the handwriting on the gravestone and the size/shape of the gravestone that's drawn in the comic book completely change between shots.
Continuity mistake: When Mrs. Hastings is on the phone abut the tree in the garden, her phone is not in call mode.
Continuity mistake: When Lieutenant Tanner has all the Liars lined up at the station, she says that she's giving them a chance to tell their side of the story before her side becomes the only side. As she says this, Aria can be seen scratching her head in the reflection behind Tanner. In the next shot however, both Aria's arms are suddenly folded.