They seemed to think they had put into place some sort of magical process improvement that would keep them from pain you always have getting a big project like this going. They only planned two weeks for an integration task that has been going for close to 2 months now and will probably continue through the end of the year. Things are 'mostly' working now, just not quite. Each individual calculation seems right, but the composite shows too much error and breaks the system. So, they are digging down into everything to try and find the cause of the error.
Of course, in order to do that, they had to model the system in Matlab(which they should have done BEFORE writing the requirements). Now that they have some of those piece in place, they are scrutinizing the guts of everything which requires answering lots of questions about how and why stuff was done(I didn't code it, how would I know, I'm basically being asked to act as a psychic or BS artist).