Other mistake: When the dowager visits Matthew in his bedroom to tell him Mary is still in love with him before he goes through with marrying Lavinia, the curtains hanging behind Matthew are so wrinkled and creased just as curtains are when they come out of a package from the store. The crease lines are terrible! One would think set design would have steamed them as in real life, they would have been custom-made and certainly not folded up like that for shipping, thus never having creases like that.
Other mistake: At the end of this episode after Edith is jilted at the altar, Albert makes some rather "home boy" comments about the food and then asks if there is any cheese to eat as if that's all he's used to or wants. This seems inconsistent since for the rest of the series Albert is the guy who seems to appreciate well-made food and wants to be a cook.