The seriousness of this depends on the consequences of the failure and how much of the time the lock is held. If the failure causes double charging a customer t

The seriousness of this depends on the consequences of the failure and how much of the time the lock is held. If the failure causes double charging a customer that's likely far more serious than if it double emails a customers. And if the lock spends most of its time not held then spotting a doubling of its message can probably be spotted and fixed far more easily than if the lock spends most of its time held.