"We think the two periods of time when there was a sudden drop in trading (9:48 and 9:52) are when they restarted the system. Once it came back, the Tester, being part of the package, fired up too and proceeded to continue ..."
Ouch!
Ouch!
But creating a bug that loses your company half a billion dollars in thirty minutes and bankrupts them, must be stomach-churning.
This is a risk management failure much more than a programming error.