They just posted on Twitter about it: https://twitter.com/coinbase/status/964248915695448064
And then they flurried to update things. Like the parent says, multiple issues for at least a week, and the first communication is responding to (some) people on Reddit, and only after they're called out do they think "Shit, we should probably tell our other customers, too". Wonder how many wouldn't have noticed?
Not exactly. They are referring to "some customers recently were charged incorrectly". They identified the culprit as the MCC change which they call "downstream" of them.
The only thing that makes me think the current MCC message might not be relevant is that Reddit users seemed to be reporting multiple ACH charges against the same checking account. The previous MCC category change messaging suggested it would only affect credit cards. Perhaps that category change affects how the ACH API responds and the CoinBase system interpreted it as a "needs retry" kind of state.