The Crab with the Golden Claws: Part 1 - S1-E1
Other mistake: After Tintin and Snowy run out of the room containing Mr. Kuraki, they are discovered by Allan and the two bad guys he is with. The three of them then take their guns out, aim them at Tintin and Snowy and begin to shoot them. The bullets miss Tintin and Snowy and end up hitting the wall. No bullet marks are ever visible in the wall after this. (00:14:25)