I don't know if anything has changed, but last time I tried codegen for Common Lisp, the LLM would routinely mix up LISP dialects and language specific features.
Less so with Clojure.
It used to happen last year but really isn't a thing anymore (assuming you use frontier models).
I've been using LLMs for Common Lisp since Sonnet 3.7 and have never experienced that. Did you have a mixture of other lisps nearby to confuse it? Seems like an odd failure mode.