The component in question is the recovery sequencer. It does exactly what it’s name implies. It sequences the recovery once the seat leaves the aircraft. The egress troops in the field do not open this device.
Evidently there were electronic components inside the recovery sequencer on this particular seat that did not meet requirements. It sounds to me that this particular seat was delivered with the faulty RS, or, faulty components were pt in the RS during depot level maintenance. No front line maintainers or aircrew had any reason to doubt it’s integrity.
In this particular case, the pilot ejected from the aircraft successfully, but the recovery sequencer failed. He never separated from the seat and died on impact with the ground.