According to the latest lines I've heard mentioned about the 720s, they are not running late and are taking the same amount of time to build as was expected to build, as there is no problem with the software, design of performance of these new trains.
The reason that the trains are not entering service on the previously estimated date, is because of an earlier batch of similar trains that were built for Transport for London had some issues with operating with the infrastructure on other lines and this meant that the building of the new units for Greater Anglia had to be pushed back, but there is no problem with the Greater Anglia units and the time it takes to build each train has not been delayed.