Here's an edited version of the answer.
Is there anything you have ever written in the Briefing that you think should be retracted?
When I type 'Cheng' into the Briefing search engine it gives me a list of articles I've written, although not, perhaps unfortunately, with the words of heresy in red.
I am not specifically aware of anything I've written that falls into the category of 'heresy', but undoubtedly there is material there that is questionable in emphasis or misleading, and would possibly even best be retracted or not written. I still don't believe in daily prayer times (Briefing #337), however on reflection that might be an example of something not helpful to some readers, and best left unsaid. OTOH, some nice readers did write in to set me straight on that, so the Briefing does have a mechanism in place for public and private rebuke of things that cause concern.
But when I say there is 'undoubtedly' stuff there that could be retracted, it is more because the Bible assures me that I am completely tainted by sin in every area of my life, and gives no corresponding assurance that this sin is overruled every time I put finger to keyboard. So far, no-one has accused me of writing heresy, to my knowledge, although it could be that they tried and I didn't discover this for some reason.
I do remember writing an article some 15(?) years ago tentatively suggesting a gradualist view of abortion, which view I deeply regret and repent of. And I am thankful to God and Tony Payne that it never saw the light of the Briefing day. But as it didn't make it in, it doesn't really count as an example I think.
There was a time, too, in the early '90s where I thought that NT Wright's views on justification were worth paying attention to, and they may even have slipped into some talks I gave. Never caught the full disease, it was more like a low-grade virus that slowed down my performance in all areas. But once again, in the mercy of God, that sort of rubbish was consigned to the Briefing's editorial garbage bin, if indeed it even made it into a draft article. Thank God, I was delivered from at least one form of theologically complex and prolix obfuscation, if not all.
It'll all be exposed on judgement day, of course, as to whether the articles written were written with gold, silver, precious stones, wood, hay, straw or paper. Then both you and I will have an answer to the question.