The incubation period for chicken pox is approximately 2 weeks. There is no way the PR executive got chicken pox from the child next to her on the plane the day before.
Prince Colin's deceased father is referred to as the "monarch". This would mean that Colin should have automatically become king upon his death. Either Queen Rosalind was the consort to His Majesty - or he was the consort to monarch Queen Rosalind. They can't both be monarchs, and the consort cannot become the new monarch upon their spouse's death.
At the end they are waltzing to "I'm Gonna Keep on Loving You" by Reo Speedwagon. The song is written with a 4/4 beat. A waltz is done to songs that are 3/4 beat. It wouldn't be possible to waltz to that song.
When the microwave timer goes off and she goes to retrieve her food, the display simply shows the time. Had the microwave actually been in use it would read "READY" or something similar. Correction: This is only true if it's a commercial oven for public use. Most consumer ovens return to the clock screen.
Prince Colin and Penelope (and one or two minor characters) keep misnaming Deidre as Deirdre. They change their pronunciation from Deirdre to Deidre only late in the movie.
At the queen's jubilee Prince Colin is in military dress despite having not served in the military.
Clearly Mandy is shown to be working in New York City but earlier in the movie, she is getting food from a food truck and the license plate of said food truck indicates that it is from Georgia.
Taylor Cole is five foot eight inches and Lauren Holly is five foot five inches and yet the clothes meant for Lauren fit Taylor perfectly.