I mean, if you were hoping to use the API to generate something machine-parse-albe, and that used to work, but it doesn't any more, then sure, that's a sort of regression. But it's not a regression in coding, but a regression in following specific kinds of directions.

I certainly have found quirks like this; for instance, for a while I was asking it questions about Chinese grammar; but I wanted it only to use Chinese characters, and not to use pinyin. I tried all sorts of prompt variations to get it not to output pinyin, but was unsuccessful, and in the end gave up. But I think that's a very different class of failure than "Can't output correct code in the first place".