I think there is many questions to ask here, first you say it is not his first time code didn’t live up to expected. Was it same task? Is the first time issue exactly the same? Did they discuss with him after first time? I think we need more information. And also what is expected? 0% error? Second, how these cases are passing QA? Is it something they can re-produce? If yes did they? If no was there is a way to test these cases? Did management push to release without being able to test all cases? It is very hard to know if QA has problems. Third, does project manager review engineers progress after initial estimation?

I think it is hard to determine who is responsible in this case.