At the very beginning of the movie, Brooke is serving food at a party and one of her heel breaks. She is limping from the different heights of her feet, so she then takes off both shoes and kicks them under a table. As she turns, she immediately speaks to the person giving the party, and walks away obviously limping once again, as though she never took her shoes off.
The Baron sits to down to the piano and the captions say he plays the 12 days of Christmas. But he plays Holly and Ivy.
There are no Earls and Duchesses in Ireland, and no Irish person would ever use those honorifics. The Irish Constitution eliminated all titles of nobility when it became independent from Britain in 1922.
All of the exterior scenes of the castle decorated with Christmas lights and wreaths look fake and unreal.
During the horseback riding scene, the background doesn't move correctly with the foreground, due to poor CGI workmanship.
While in the car with Aiden, Brooke gets a call from Margot, warning her that the journalist is at the castle. Margot hangs up the phone while Brooke pretends to continue the conversation for a few moments, but Brooke's phone still shows her on an active call.
When the Irish dancers perform at the party at the end, there's a close-up of their dancing feet. The woman on the right is on the wrong foot and messes up the choreography.
The Baron plays a few strains of "The Holly and the Ivy" for Brooke and Aiden but the captions identify the song as "12 Days of Christmas."