Ref :The major error seems to be the upgrade shortly before, adding potential (military) inputs. A correct upgrade process should have identified those added inputs, and stress tested the system with those added inputs against maximum previous inputs.
I don't know the details but suspect that it was thought that the few added military consoles would still be well within the limits. It was not at that time recognised that leaving consoles in watching mode made the software see more than the linmits. Thus they did not test for max number of consoles plus max no. of watching consoles. A failure of imagination or just complete lack of knowlege of what watching consoles did??