Factual error: Will's hospital chart states he is taking Warfarin and Coumadin. These are both the same drug to prevent blood clots. He would not be on both. (00:31:50)
Factual error: The 1725 issue of 'The Haven Herald' used as part of every episode's title sequence is packed with errors. It is written in modern English, with some very modern turns of phrase (e.g. Had it with this town, get on with her life). The same paragraph appears twice. It is headed "Haven, Me." - Maine was part of Massachusetts until 1820 and the abbreviation was not commonly used at all until the 20th century. And it costs 2 cents - until 1793 British-style pounds, shillings and pence were used throughout America. Also, February 18th 1725 was a Sunday, not a Tuesday.
Audrey Parker's Day Off - S2-E6
Factual error: When Audrey turns on the car radio to listen to the baseball game score, the LCD display turns to the time. When she turns it off, it shows the tuner. This is the opposite of how car radios function - the sound editor must have been dubbing in the sound, and missed this).