Red Rackham's Treasure - S1-E5
Deliberate mistake: Haddock draws an X on the shark image of Calculus' box with a pencil. This was done as a visual gag, though the X mark is far too thick for the pencil that Haddock was using. (00:07:00)
The Black Island: Part 1 - S1-E10
Deliberate mistake: Tintin gets his leg stuck in a man trap. All scenes after this show no ripping in his socks. (00:14:40)
The Secret of the Unicorn: Part 1 - S1-E3
Deliberate mistake: After Francis Haddock kills Red Rackham, he lights a fuse to the explosives. The fuse that was lit is only a foot long, yet he is somehow able to climb out the ship without anyone noticing, get into a boat and swim all the way to land before it explodes. At a foot long it would have exploded in 10 - 15 seconds, all of that would taken at least 10 minutes. (00:18:45)
Chosen answer: If Hector was seriously intent on removing King Ottokar's scepter from the glass cage holding it and launching it through the window with the camera, then Hector would have been forced to knock out the two guards so they would not have interfered with Hector's plan as soon as he removed the scepter from the glass. As for Hector, himself, was explained when Tintin was explaining how Hector stole the scepter. Tintin placed a twig inside the camera and it launched out of the camera. Hector would have placed the scepter inside of the camera, and would have been knocked unconscious due to the spring effect created when the scepter had been launched.
Casual Person