Partly that (I think there were some legacy systems that were missed), partly that every minor clerical and drawing error that got passed through because of how

Partly that (I think there were some legacy systems that were missed), partly that every minor clerical and drawing error that got passed through because of how insignificant it was (nothing that would affect the integrity of the aircraft I should add) has been flagged by Boeing. They want to look proactive to their customers and shareholders I suppose. That means lots of tiny, insignificant changes to hundreds of drawings. It's nothing technically challenging for the most part - just lots and lots of paperwork.