Other mistake: In modern time Natalie Vasquez dies in episode 13 and her character is just discontinued. In flashbacks after that episode she's never seen again. She's not even seen at the graduation day of the trainees, but we see her at the Grand Central bombing, which supposedly happened just days after the trainees became agents.
Quantico (2015)
1 other mistake in Season 1 generally
Starring: Aunjanue Ellis, Priyanka Chopra, Josh Hopkins, Jake McLaughlin
Character mistake: The diploma on the wall in Connor's office for the University of Kentucky, "university" is misspelled "universisty".