During the drive to the first archaeology site, the position and clothes of the passengers are different from when they first drive off.
Throughout the movie the archaeological team alternates between needing a translator and speaking the local languages.
When buying the donkey, Chapman mentions the boy's name. However the boy's name is never mentioned and Chapman doesn't ask the boy his name. So there was no way of him knowing what it was.
During the banquet thrown by the local sultan, Chapman is seen eating a piece of roast meat with both hands. This would be a major faux pas, since only the right hand is used for eating in desert Arab cultures.