How do I add a bar to the end of a rthm-chain? The add-bar method returns an error.

(let* ((rch (make-rthm-chain
	     'test-rch 23
	     '((((e) e)			; 4 in total
		(- s (s) (s) s -)
		({ 3 (te) - te te - })
		((e.) s))
	       (({ 3 (te) te (te) })	; what we transition to
		({ 3 - te (te) te - })
		({ 3 (te) - te te - })
		({ 3 (te) (te) te })))
	     '((((q q)			; the 2/4 bars: 5 total
		 ((q) q)
		 ((q) q)
		 ((q) (s) e.)
		 (- e e - (e) e))
		(({ 3 te+te te+te te+te }) ; what we transition to
		 (q - s e. -)
		 (q (s) e.)
		 (q (s) - s e -)
		 ({ 3 te+te te+te - te te - })))
	       ((((e.) s (e) e (s) e.)	; the 3/4 bars: 4 total
		 (- e e - (e) e (q))
		 (- e. s - - +e e - (q))
		 (q (e.) s (q)))
		(({ 3 (te) (te) te+te te+te } (q)) ; what we transition to
		 (- e. s - (q) (s) - s e -)
		 ({ 3 te+te te } (q) q)
		 ({ 3 - te te te - } (e) e { 3 (te) (te) te }))))
	     :players '(pno pnol)
	     :slow-fibonacci t
	     :activity-curve '(0 1 100 10)
	     :harmonic-rthm-curve '(0 1 100 3)
	     :do-sticking t
	     :do-sticking-curve '(0 1 25 0 50 1 75 0 100 1)
	     :sticking-curve '(0 0 100 10)
	     :sticking-repeats '(3 5 7 11 2 7 5 3 13)
	     :sticking-rthms '(e s. 32 e.)
	     :split-data '(4 7))))

  (create-psps (palette rch))
  
  (make-slippery-chicken  
   '+mini+ 
   :title "Your Title Here" 
   :composer "Your Name Here"
   :ensemble '(((pno (piano :midi-channel 1))
		(pnol (piano-lh :midi-channel 1))))
   :staff-groupings '(2)
   :tempo-map '((1 (q 60)))
   :set-palette `((set1 ((b2 a4 d5 e5 a5 d6))) 
		  (set2 ((b2 fs3 d4 e4 a4 d5 e5 a5 d6))))
   :set-map `((1 ,(loop for i below (num-rthm-seqs rch)
		     collect (if (evenp i) 'set1 'set2))))
   :rthm-seq-palette (palette rch)
   :rthm-seq-map rch)

  (add-bar rch (make-rthm-seq-bar '((5 8) e e+32 s. +q)))

;;; Output
  (midi-play +mini+)			; midi file
  (cmn-display +mini+)			; score display
					;(lp-display +mini+) ; lilypond display
  )