Could be the spring housing. But why not just open it up and have a look? They’re really quite easy to strip and rebuild, with parts quite easy to get hold of. What’s the worst that can happen! :0)
Quite a few 10 speed videos available on YouTube, this is the best one I’ve seen to date.
Judging by the text on this link, to me 9 speed sounds extremely similar.
(also a link to official Campag rebuild instructions at the bottom)
My only doubt is that as they are a model slightly lower down the range that they might not be repairable, but I’ve not found anything on the internet to either prove or disprove this.