Perhaps related to the message thread "Possibly invalid test cases":

fixnums.sls currently has

   (define (fxbit-field-rotate i count start end)
     (if (fxnegative? count)
       (fxrotate-bit-field i start end (+ count (- start end)))  ; <---
       (fxrotate-bit-field i start end count)))

the marked line should probably finish  (- end start)  to yield a
positive count for fxrotate-bit-field.

With that change, test 202 passes on Chez Scheme, along with all the
other tests.

--
Peter Lane
http://peterlane.info/scheme.html