There seems to be an issue with rationals as rhythm values when trying to write cmn, lilypond or xml data. Here is a minimal example that produces a weird score:

(let* ((working-title
	(make-slippery-chicken
	 '+working-title+
	 :title "working-title"
	 :ensemble '(((oboe (oboe :midi-channel 1))))
	 :set-palette '(( 1 ((c4))))
	 :tempo-map '((1 (q 90)))
	 :set-map `((1 (1)))
	 :rthm-seq-palette '((1 ((((4 4) 4/3 4)))))
	 :rthm-seq-map `((1 ((oboe (1))))))))
  (cmn-display working-title)
  (lp-display working-title)
  (write-xml working-title))

With cmn, the 4/3, which should be a dotted half note, becomes just a half note.
Lilypond writes a whole note and the following quarter into a second bar, which shoudln't exist.
When opening the xml file with musescore I see a whole note and a quarter in one 4/4 bar.
For me there is no error or warning within sc.