Just had one today where GPT-5.4, instead of adding the 10 lines I asked for (an addition that could be done pretty mechanically by just looking at some previous code and adding a similar thing with different/new variable names) proceeded to rewrite 50 lines instead, because it was "cleaner". It was not. It also didn't originally add the thing I asked for either, which was perplexing.

Over-editing is definitely not some long gone problem. This was on xhigh thinking, because I forgot to set it to lower.