If you have a search in the forum - I think you will find 'several' posts re core plugs - apparently it is very common with the Nelli's
When mine was in for a service at Bennetts earlier this year - Russ noticed they were leaking so replaced them (again under warranty)
I cant remember who it was - but they bought a tornado - did a track day pretty soon into the ownership and the core plug went either just as he got to the track or just after the 1st session (I think)
Its nothing to worry about- just one of the quirls owner an Italian Brand !!