What worries me is the text mentions specifically that their was a "final termination order". Maybe that is hardwired list of internal orders as a failsafe but it doesn't quite fit. Why destroy yourself and not simply power down, that's wasting all those potential post-war spaceframes?
Because if, hypothetically
if, this was a contingency, it'd be a contingency only intended to activate i a very specific situation.
If somehow
everything went wrong and no Vehnen entity was in any position to control the automatic weapons, the things would eventually immolate themselves up rather than turning into a berserker plague capable of destroying the galaxy... long after it would have long since ceased to matter to the Vehnen.
Presumably, the Vehnen had other measures in place to reassert control more conventionally, and they all failed. It is not certain, but is far from impossible, that when the proto-berserkers were being designed, someone had the rather altruistic foresight to hardcode in something that would keep them from completely wiping out all life in the galaxy if they somehow got out of control.
And why such a random number of years before hitting the big self-destruct button?
Notably, it might be a random number of years to us, but a very significant number to the Vehnens. We don't know from the information available either the length of their preferred standard year, or their numbering system.
We might set an automated system to self-destruct after, say, 1000 years, but to an alien species that might be 1192 years and 73 days, an arbitrary number picked for no readily apparent reason.
They are killing machines not thinking machines if the orders are to land on the nearest Sun then they can't exactly disobey.
Yes, but that's not the question; the question is
where the order came from. Because either it was pre-coded into them ("if your central command node receives no orders from any Vehnen entity for X centuries, self-destruct"), or someone found a working system capable of issuing the self-destruct code directly.
Hm. I wonder how the Cube fit into all this. We may never know now, I suppose.