I think that the spec file have typo, missing parenthesis:

(chain xs
       (map (lambda (x) (+ x 1) _)
       (filter odd? _)
       (fold * 1 _))

Missing closing of lambda.

I think it should be:

(chain xs
       (map (lambda (x) (+ x 1)) _)
       (filter odd? _)
       (fold * 1 _))