Sk80 clubman chuck

Hi gang, wondering if anyone can help. Iv several sk80 and sk100 clubman chucks been using them for about 18 months with out fault. Recently when tightening one of the sk80s it has started to spin where the tip of the chuck key fits in, rather than the thoothed part spinning, so when tightening its physicaly moving my hand towards me ( mainly towards the end of tightening up ) Its not having any issues holding work in the dove tail jaws but im concerned as to why its doing this, if its a sign its on its way out or needs a replacment part. Any help would be grwatly appreciated.

I would suggest that something is coming loose inside the chuck, but if they’re only 18 months old Axminster will sort it out, give them a call.