At the end of the episode, while talking to Tony, Abby shuts down the elevator, saying she's never done it before. However, she did just that in "Rule 51," while strategizing with Tony and Ziva about how to get Gibbs out of Mexico.
When we first see Tali in the park, her legs are sticking out and she has no blanket on her, yet in the side view scenes between Tony and Tim her feet can't be seen and there is a flat pink blanket where Tali is supposed to be.
When the "Tribute to Our Fallen" display is shown, it includes Paula Cassidy, Simon Cade, Gayne Levin, Jenny Shepard, Tom Morrow, Caitlin Todd, Brent Langer and Ned Dorneget. Noticeably missing is Christopher Pacci who died in the line of duty in S1, E19.
Abby says the mud "tested positive for isotopes." This means nothing. An isotope is just one form of an atom with a particular number of neutrons. Literally every atom is an isotope. Not all are radioactive, though, which is likely what Abby meant to refer to.
Abby talks about air speed velocity. There is no such thing. It's either air speed or air velocity.