I don't recall ever hearing that Facebook made a mistake which decreased the amount of data they collected or their usage thereof. Can anyone provide an example?
I get what you’re getting at here, but I don’t think it would be reported in the general media as it’s not a privacy violation.
I'm sure Facebook has had bugs that broke various forms of data collection, or missed data they could have collected. We wouldn't hear about it, but it would be surprising if it hadn't happened.