More seat-of-the-pants script changes
It was Christopher McQuarrie, one of the better writers out there, and a guy who has been called on to quietly fix major motion pictures before (most famously: World War Z). According to my sources McQuarrie came in fairly early during shooting and used his Usual Suspects/Mission: Impossible skills to tighten up and fix this heist story set in the Star Wars universe. It's unlikely that McQuarrie will get a credit on the movie, although one source used the word 'saved' when talking about McQuarrie's contribution to the film.
Prediction: The heist fails. A new plan is formed to put R2-D2 on the Death Star to download the plans.