Anachronisms
Lord Grantham accuses Tom of being a "hater" in one episode and Lady Grantham used "to parent" as a verb in another. No one talked like this in the early 20th century. I'm sure there are many other such verbal anachronisms, but those are the ones that I just noticed. I found it irritating and it threw me out of the story world completely. I don't want to hear the Granthams talking like Dr. Phil.