Plot hole: It turns out in the climax of the episode that there are no bullets left in the gun and Miss Fisher knew it. That would mean then that she deliberately wasted minutes with Simon bleeding out on the floor when Chaim was holding them at gunpoint with an empty revolver, for no discernible purpose.
Episode #4.1 - S4-E1
Plot hole: When DCI Roz Huntley kills Forensic Coordinator Tim Ifield the crucial piece of damning evidence is her DNA under his fingernails after scratching her arm. Problem being, at the time of his murder, he was wearing surgical gloves. (00:56:40)