The necklace and bracelet that Candace Cameron Bure wears throughout the movie actually belong to her 90-year-old grandmother; they were purchased by her grandfather in the 1940s.
One of the police officers says, "I've never heard of a Hudson", standing next to another officer played by Oliver Hudson.
A little under a year after the film premiered, on October 17th 2017, it received a novelization by Leigh Duncan, released as the first e-book from the recently launched Hallmark Publishing.
Jake (Oliver Hudson) mentions to Sarah in the police station that drivers licenses weren't invented until the 1930's when in fact Europe had driver's licenses as early as 1903 and the US had driver licenses as early as 1910. New York required chauffeurs to get licenses and then in 1913 New Jersey became the first state to require a license but it wasn't until 1934 that driving laws came into effect.
Comets don't suddenly appear. They are generally visible for months, slowly getting brighter and getting a longer, more visible tail as they near the sun. What was displayed in the movie was more of a shooting star(meteor) in appearance.
Malmedy where the husband was in the war is in Belgium, not in France like she says.