Originally Posted by
tdracer
Just thinking out loud here, but:
AP based solid rocket propellant is very stable and stores quite well (in my amateur rocketry activities I've successfully used AP propellant reloads that were 20+ years old), with one exception:
It can become very difficult to ignite. A layer of oxide often forms on the exposed surfaces which interferes with the ability of the igniter pyrogen to ignite the propellant. This can result in one or more of what we call a 'chuff'' where the propellant partially ignites (resulting in a 'chuff' of exhaust), then a pause while the chamber pressure/temp come back up and either it 'chuffs' again or it properly ignites.
Perhaps an decades old ejection seat rocket motor didn't light cleanly?
Except I don’t think this type of seat has a rocket motor.