Episode Two: Sky and Arby are in the school library and decide to "borrow" an atlas. Arby is holding the book as he goes through the door to the corridor but does not have it when they emerge on the other side. To cover this mistake, episode three has Roy return to the school to pick up a torch his father has dropped confronting Sky and he finds the atlas on the corridor floor.
Episode seven: Arby does not want Sky to leave because he says Sky promised him a vision of the future. Sky never makes any such promise in the script. The promise appears to be tacked on so as to give Arby a reason to follow Sky into the Juganet.
Epidode four: In the consulting room scene with Goodchild and Dr Saul, the boom practically rests on tall Goodchild's head.