Character mistake: When Jack and Kate are in the car discussing the fact that the Russian agents found him because of Mark Boudreau, Kate wrongly refers to him as Martin Boudreau.
Character mistake: The brigadier wears a regimental cap badge. Colonels and brigadiers have their own cap badge.
Episode #6.4 - S6-E4
Character mistake: The character pretending to be Lt. Ellis refers to himself as First Lieutenant. That rank is referred to orally as "Lieutenant", not "First Lieutenant."
The Prison Prep School Murder Case File 1 - S1-E10
Character mistake: To show how hard the top students are working at the prep school, we see one of them writing; "I was at the course of a eight-week intensive." (00:04:50)