Blood disappears and reappears on the neck of Lee Chung (other captive) when Ressler has him pinned to the tree.
In the car scene in Alaska where Donald Ressler is speaking on his cell phone, he is speaking to the back of it.
Ressler slams the car door on his thumb, but the sound effects guys dub the sound of the door closing.
Tom Kemp is listed as "Anchorage Sheriff, but Anchorage has no Sheriff. As a municipality, the city of Anchorage police department has a Chief of Police and no Sheriff's Department.
When looking at the chess game, Reddington says "Queen to B4, check". The man playing black then moves his queen from C8 to B8 check and wouldn't have been able to move to B4. The white queen, however, is on D2 and can now move to B4 to block the check and also check the black king. Reddington would have to be assuming black's move in order to predict white's next move, but he moves away before white moves, possibly because he didn't realise it was black's move, not white's.