Episode #1.3 - S1-E3
Other mistake: The publican asks for payment for some drinks, saying "One and six, please", meaning one shilling and sixpence. The subtitles say "One-o-six, please."
Episode #8.2 - S8-E2
Other mistake: Paulie takes off his blood-soaked shirt at the laundry. His undershirt is clean. It should also be covered in blood.
Episode #8.5 - S8-E5
Other mistake: We are told several times that the "Special Reserve" is kept locked in Mr. Palmer's office. When Anna comes to the bar to "see" it (and put the poison in it), it is in plain sight on the shelf behind the bar, and her husband hands it to her.