Does same work ok in standard joomla core SEF ?
If it works ok with joomla core sef, it's a sh404sef issue,
if no, then we should look into it.
But as we use same CBSubs and CB and joomla core sef on this site, and we don't have issues...
CB uses standard joomla sefing for urls.
Please let us know the result of the test above