Oh, and from what I've read about forgetting to oxygenate wort. If you're pitching yeast starters, or dry yeast, the oxygenation isn't AS important. I'm not sure if you do starters—you should if you dont. I'm guessing at least one of ten batches was pitched with dry yeast. If that's the case and you still got the flavors, I'm guessing it's not the oxygen.
Another thing, do you let the beer sit on the lees for extended periods of time? I know you transfer to secondary and cold crash for four days, but do you of let the beer sit in primary for long periods of time? It's claimed that after 45 days or so on the lees, off flavors start to happen.