The Star Wars spin-off film that bridges the events of Episode III: Revenge of the Sith and Episode IV: A New Hope, apparently needed to draw on the powers of three writers to reach the bar that Disney set for the film. According to Latino Review, Christopher McQuarrie, the writer behind Mission: Impossible – Rogue Nation and The Usual Suspects, was hired to 'beef up' the script.
Rogue One: A Star Wars Story was originally scripted by Gary Whitta, who was revealed have completed the project in January 2015 and would be stepping down. Following Whitta's departure, Chris Weitz took a crack at the film.
Those two writers didn't seem to get the job done right. If sources are correct, McQuarrie did a 'two-week polish' on the script. Whether or not this is true remains to be confirmed by McQuarrie, Lucasfilm or Disney – so consider it hearsay at this point. A film crafted by three writers should prove to be interesting… hopefully, it won't bring any continuity issues along with it.