Revealing mistake: "The Creature's Revenge" (Adventure 3, Part 2): This apartment building has unbelievably clean elevator cables. Steel takes off his coat and then ties a knot in the cable - without getting a single grease smudge on his hands or his pristine white shirt. (00:06:45)
Revealing mistake: "Dr. McDee Must Die" (Adventure 5, Part 3): When the champagne glass shatters in front of Sapphire, you can see the mini explosive charge used to break it. It lands on the table among the glass shards. (00:10:00)
Revealing mistake: "Railway Station" (Adventure 2, Part 3): Steel orders Tulley to light all of the abandoned station's lamps with matches. But after the lamps are lit, they give off a steady illumination and don't flicker. It's obvious that they all have electric bulbs in them. (00:11:00 - 00:15:00)