The armored truck shown near the end of the episode has "ordinary" California license plates. It should have commercial plates. Even though they're fictitious numbers, they should be the right style of fictitious numbers.
Chris O'Donnell's ring is visible while Callen is holding his gun toward the end of the episode. It is in fact not his wedding ring, but his character's. Callen is undercover as a Canadian businessman, "Gordon Taymis" is married, his wife and kids live in Vancouver.
When Eric and Dominic bring Alex Walder's information up on computer screen, the picture of him on the left is a white man and the military ID on the right has a picture of a black man. The white man on the left is Valdivia, the victim from the case.
When Alex's car is pulled from the water without it's bonnet (or "hood") there is quite clearly no engine in place.