The Night of the Plague - S4-E24
Other mistake: In the last fight scene, West runs uphill from the cave entering the scene from the most east side of the screen. There is a bad guy on the ground to West's right side as West is running uphill. The villains chase West, but their shot shows them entering the same scene from the middle of the screen with the guy on the ground on their left side.
The Night of the Plague - S4-E24
Continuity mistake: The last scene shows the back of the boxcar amid dirt and brown/mustard colored short grass. When Ms. Averi Trent opens the door to meet her fiancé, we see a lush green tree by the door.