Grand Hotel - S2-E7
Factual error: A hotel worker citizens arrests a guy for statutory rape in his hotel of his girlfriend who is 17. The police talk about charging him but not wanting to. 17 is legal age of consent in New York so there would be no statutory rape.
Uniform Day - S6-E17
Factual error: It is Uniform Day where they all have to wear their uniforms. The badges they all wear are those of patrolmen. The problem is that they are detectives and the NYPD has detective badges, which are distinctly different looking.