Send it back to gravitydropper. Seriously, mine was getting a bit tired then the bar clasp broke. I dropped GD a line in the US and asked them about spares.
They just said send it back and they'd look at it. Within 2 weeks the post was returned completely refurbed. Only original part on it is the post shaft. All for a tenner postage.
Amazing customer service. The post is 2 years old and now works like new again.