I think the error is in use of "src" arg to make-seq in the following loop,
in ice-9/psyntax.scm, starting at line 1633:
(let lp ((var-ids var-ids) (vars vars) (vals vals)
(tail (expand-tail-expr)))
(cond
((null? var-ids) tail)
((not (car var-ids))
(lp (cdr var-ids) (cdr vars) (cdr vals)
(make-seq src ((car vals)) tail)))
(else
(let ((var-ids (map (lambda (id)
(if id (syntax->datum id) '_))
(reverse var-ids)))
(vars (map (lambda (var) (or var (gen-label)))
(reverse vars)))
(vals (map (lambda (expand-expr id)
(if id
(expand-expr)
(make-seq src
(expand-expr)
(build-void src))))
(reverse vals) (reverse var-ids))))
(build-letrec src #t var-ids vars vals tail)))))
