E002 is trying to complete stage 5 testing, 10,000km of mainline test running of which 2,500km is fault free. #3 is on stage 4, which is wider network testing and working towards stage 5, only having to complete 4,000km with 2,000km fault free. #4 is on stage 3 which is running on the Pakenham line working up to stage 4. #5 to 13 will be undergoing stages 1, testing of mechanical and electrical components, and stage 2, testing within the depot at East Pakenham with the aim of getting to stage 3 asap. Not working at that depot I can't say how many are at stage 2 but I doubt that there are many sitting around having nothing done to them.
If #1 had passed stages 1 and 2 it would also be out on the Pakenham line working on stage 3, IMHO. The fact that it isn't points to its failing one or more of those stages, which corrolates with the reports of electrical problems.
PVcommuter's comment about not disrupting the supply chain makes prefect sense about fixing #1 only when the pressure is off the production line.