Incorrectly regarded as a goof: Thomas sometimes appears and disappears instantaneously, but sometimes he fades in and out. Although cited as a mistake, this is actually intentional. Thomas' abilities and mannerisms are highly fluctuating, reflecting his erratic character.
The gun sound effects in the movie are factually incorrect; a truly suppressed firearm does not have the sound used in the movie.
During the break in at Gavin's house, you can see Director Garrett Thomas briefly in a mirror when Sumrall and Thomas are checking Gavin's master bedroom. Also, during the break in at the CIA black site, you can see crew members: camera people in reflections near the beginning of the sequence, and crew on the other side of the glass during the final confrontation in the lobby.