The Gang Gets Held Hostage - S3-E4
Continuity mistake: When Frank and Charlie are coming out of the vent and onto the roof there is no gun taped to his upper back, he walks up to the Mcpoyles and a gun is magically taped there. (00:19:40)
The Gang Gets Held Hostage - S3-E4
Revealing mistake: When Liam is stabbed in the arm, as he turns around to walk away, you can see the outline of his real arm wrapped behind his back, under his robe for about one full second, revealing that the arm he was stabbed in was a fake prop-arm.