As someone who works on software for one of the automakers, I also want to note that there seems to be a lot of focus on the software... but it's also very possible the problem was with the hardware: something in the vision or sensor system was incorrectly installed, defective, was calibrated incorrectly, lost calibration during use, etc.
I'm sure the software can always be improved, but if most cars are driving through this stretch without a problem and his always veers, that sounds like something unique to his vehicle which points to hardware in my opinion. In cars, the software can only ever be as good as the data it receives.