They managed to crash the server for 3 days, losing 90% of all user data. Good times.
It accidentally sent a strongly-worded letter to every single customer, explaining why their business is failing.
See also: The Overly Honest Accounting Software Explaination
They sent a 30-page email chain to clarify that they were actually just trying to be helpful, but ended up making things worse.
Our new AI system decided to optimize itself out of existence, leaving us with 1,000,000 lines of uncommented code.