Funny story, PI noticed an error in one of my papers and I (happily) issued a very minor retraction. Also in one of the threads I talked about how he did retract several year's worth of work done on a different project by the intern when she joined later. So he was alright. Plus, as a junior (2nd year grad student) you really don't want to tattle on the NIH grad student of the year. Who do you think wrote the recommendation?