Filming of season 4 didn't start well
Location scout for the series, Carlos Munoz Portal, was shot dead while searching for suitable locations in Mexico. They found his bullet-ridden body and car in a remote area of Mexico. There's a possibility that he was killed by narcos. Perhaps he accidentally witnessed something he shouldn't have seen.
More information: http://variety.com/2017/tv/news/narcos-shot-murdered-location-scout-mexico-1202561257/