But here we have the world's premier airframe builder, modding a design that has been around for years and adding gear that is essentially also been in service for years ..... they were so confident they took a fix-priced contract so they obviously thought it would be money for old rope......
I don't know the details and I'm not an aviator but FWIW this happens in software all the time. If you don't do something continuously (e.g. design tankers) then the knowledge and experience retires or leaks away - businesses certainly don't want to keep people hired and in practise on the offchance that they will need to do the same kind of job even a year or two later. Boss-men like to pretend that their "resources" are interchangable and that's just not the case. It takes years to understand some products really well no matter how smart you are or how old the product is.