(defmacro repro ()
  (let* ((kmap-sym (gensym "kmap-")))
    `(let ((,kmap-sym (make-sparse-keymap)))
       (define-key ,kmap-sym "a"
          ',(lambda () (interactive) (message "kmap is %S" (symbol-value kmap-sym))))
       ,kmap-sym)))

(funcall (lookup-key (repro) "a"))