For example, I had it generate some C code to be used with ZeroMQ a few months ago. The code looked absolutely fine, and it mostly worked fine, but it made a mistake with its memory allocation stuff that caused it to segfault sometimes, and corrupt memory other times.
Fortunately, this was such a small project and I already know how to write code, so it wasn't too hard for me to find and fix, though I am slightly concerned that some people are copypasting large swaths of code from ChatGPT that looks mostly fine but hides subtle bugs.