KBs need the top ring larger because of the alloy and design. Not all hypers do, but KB hypers do. The second ring is not designed to be a compression ring, it's an oil scraper. So I'd have to say as BG racing said, it butted or was loose in the lands. I've broken them for both those reasons, but the bore will show sings, and that hole should need to be hit with a hone or brush. It's kinda cheap IMO to run std replacement 2nd rings as opposed to a full file-to-fit set. But this shouldnt be a problem mechanically, just cheap. Choke runs it rich. It might make it harder for the rings to seat initially if it was over rich, but you would see questionable readings on all the holes, not one.