New Recruits - S5-E2
Factual error: The contract Stone and his team force Carlton Wood and Harry Fielding to sign guaranteeing Fowler's widow the royalties from his invention for life is signed under duress and is therefore invalid. It is hard to believe that none of Stone's team know this, but it is impossible to believe that Carlton Wood wouldn't.
New Recruits - S5-E2
Other mistake: When Mickey first opens the newspaper to show the article on Fielding and Wood, in fact the article just repeats the same first three paragraphs of text again and again. (00:01:51)