Errors in geography
Between minutes 39 and 40, when Greer, Ryan and French Police SWAT team enter the building in Saint-Denis near Paris, the kid playing on ground floor sends a warning text message to Ali. The message reads '5-0' which is the way an American would warn someone. A French (speaking) kid would have sent '22'. Explanation and history can be found in French on Wikipedia by searching '22, v'là les flics !'.