[TeMPOraL]

GPT-4 tends to screw up the grammar in other languages, I imagine in proportion to inverse of the language's prevalence in the training data.

I often work with GPT-4 in Polish. I don't think I've ever had it give me an answer in Polish without at least one grammatical mistake somewhere per every two or three paragraphs. The text itself is still superb, and its command of vocabulary better than that of a median native speaker, but it revels itself by confusing genders, or forgetting about the grammatical case suffixes.