One rather prominent case would be Tailwind. v4 made breaking changes in the way Tailwind is set up, requiring different packages and syntax. However, if you ask an LLM how to set up Tailwind on your Vite & React app, it will confidently list the setup steps for Tailwind v3, which no longer work.

At times I would see people daily asking for help with their broken Tailwind setups, and almost always it was them trying to use Tailwind v4 the v3 way because some AI told them so.