Hey Helen,
I just checked, but I'm not sure what's going on. It seems that you have some kind of cache on the site. When I change a cmc file this is not reflected until I hit ctrl + f5 in the browser. And the same ´happens actually with the request. The first one goes fine and then after that the second request is cached with the values of the first one. We are storing the previous result in the session and then loading it again from the session. But in your case everything gets cached so the list synchronise doesn't work as expected. This doesn't seem to be the joomla cache. Do you have any other caching enabled on the site? Can you think of something?
Regards,
Daniel