After a week of pacing the floorboards, came to reluctant conclusion that the line managers are stlll not performing and that responsibility for the increased quality problems during the last month does, indeed, rest firmly with them.
Second-in-Charge and I have far more to do in way of running company than get bogged down in doing middle management’s jobs. Have thus spelt out to them that, from now on, it will be their jobs on the line for what comes out of their departments and that a set-in-stone system of acting on errors/under performance will now be introduced, involving a constructive mix of disciplinarians and remedial training where appropriate. Resulted in departments having immediate "riot acts" read to them by managers who are not willing to risk their jobs anymore, and one resignation. Sad about that, though had been on cards. This person had so much potential – but sometimes that’s just not enough.