With ELEC warning your tech people will likely have done a BITE on the overhead panel to see if there are any messages to begin with. With AC power available the starter should not be using battery power iirc. Possible issue with the start power unit or start control unit.
That or maybe TRU problems?
I'd be interested if/when you find out. I've not seen this myself.
Fursty Ferret, it is quite different to the bus design.