Revelations - S1-E4
Continuity mistake: Frank is at the Japanese emperor's event, and he pulls out a single action revolver with the hammer already down, a few seconds later as he's about to raise the revolver, the hammer is somehow up, and he begins cocking the hammer to make the gun operational. (00:49:40 - 00:50:20)
Continuity mistake: The officer committing seppuku is seen drawing his blade, and the katana of his kaishakunin is still sheathed. He grunts as he is about to thrust his blade, and the kaishakunin is now holding his katana in the air, ready to behead the officer. When the officer thrusts his blade into his body, the kaishakunin has a sheathed katana again, just about to draw. (00:21:05)