When Frank is telling Betty Lowe that he will continue to look into her daughter's death, but doesn't want to risk the serial killer's conviction for the murders they know he DID commit, he says there are three other victims, but earlier they said her daughter was the third victim and there were two victims that they were sure he had committed.
When Henry is telling Jack about family history, he says that his father (Jack's great great grandfather) first arrived in NYC in 1910. He became a policeman, a menial job that no one else wanted since he already knew how to shoot a gun, having been a solider in the RAF in WWI. Not only did the RAF not exist in WWI (it was the Royal Flying Corps), the war didn't begin until 1914. Since the plot narrative supports that Great Great Grandpa was in WWI, the 1910 arrival date is wrong.
When talking with the Army Major Danny says he served in the Marines. However shortly after when talking with Baez he says the Major reminds him of his drill sergeant. Marines have drill instructors and the Army has drill sergeants.