The story has a part not posted here that says they have an error rate of only 1/5th of 1%. That is extraordinary for a human operation. Still should be investigated regarding how they got the wrong information.
Snitches are why they got it wrong. Snitches tend to be people who need to feed the cops info in order to not go to prison themselves. You get the lowest of the low, trying to save their butt, being often the sole justification for a no knock warrant.
Alot of this btw is crap. Many times, you can quietly tail somebody out of their residence, detain them, then do the search. It is not quite as glamorous as flash grenades and battering rams though.