Other mistake: The date on the surveillance footage from the camera in the Russian Embassy says 01.05.08, implying that it is either January or May (depending on which date notation is being used, American mm.dd.yy or Russian dd.mm.yy). However, it is fall/autumn outside, as there are dead leaves everywhere.
Factual error: The layout of the Cox's house doesn't make sense. The house is an end-terrace - stairs on the right side (from the front). The stairs rise to the back, and perform a 180 degree turn. The first door on the left is the Cox's bedroom. The wall opposite to the bedroom door would be a solid wall - the partition wall to the neighbouring terrace. Instead it has a well lit window.
Factual error: The fitness center is supposed to be located around the D.C. area. Inside the fitness center, in one quick shot, at the top left part of the screen, out the big window, across the busy highway, you can see the sign of a camping supply store called Campmor. The one and only Campmor retail store is located on rt 17N in NJ, about 240 miles away from D.C.