Indeed, I use LLMs on some hobby Racket programs, and for Emacs Lisp, and it always messes up parentheses; then burns tokens trying to count them over and over (feels like "the number or rs in strawberry" problem).

I've found https://github.com/shcv/parenmedic to be somewhat helpful, which diagnoses parentheses issues based on when they disagree with indentation, rather than simply counting. The fact this works indicates that LLMs are paying more attention to whitespace than "actual structure".