Yes, one mistake is too many, and yes, it has happened "many" times, and for many reasons. Rarity requires comparison. You say it is not rare, yet you refuse to quantify the number of mistakes to the total number of warrant services. Why? You say more than one is too many. Using your number, you would say that 5 out of 10,000, just to pick a number, 0.05% is not rare. At what percentage of total warrant services does the number pass from rare to not rare?