When Rossi is telling Prentiss, Morgan, and JJ about the original Galen case, he says that the Galen parents were butchered with an ax, but in Birthright (2007), he tells Detective Caulfield that they were beaten to death.
When Hotch signs the divorce papers, it is notarized as having been signed by Hotch in the presence of both the notary and a witness to the signature. However, Hotch is alone in his office when he signs the papers.
Towards the beginning, Rossi is shown driving inside a mid-2000's Chevrolet Suburban with a light leather interior. However, later, it shows Rossi outside of the SUV, which is a 2007-2008 Chevrolet Suburban with a black interior.
In Birthright (2007), Rossi states that the murders happened Christmas Eve. However, the flashback scenes show no signs of it being Christmas time.
When Morgan is telling Prentiss that he "needs her cuffs" while they have the suspect down on the ground, you can clearly see that there is a pair already on the suspect.
When Penelope closes her office door in Kevin's face, the door sign reads "Sensitive Compartments Information Facility" - it should read "Sensitive Compartmented Information Facility"
In "Birthright" Rossi states that he has been haunted by the same unsolved case for 21 years, but this takes place on the 20th anniversary.