
Common thread here on GM.
General rule is that manufacturers will not deal with you - they will tell you that your guarantee has to be honoured via the shop/individual that you purchased the item from.
If you purchased them via ebay or can't get back in touch with the seller, then obviously your only hope is to try and get in touch with Dunlop.
As a last resort, getting them fixed isn't hard. It is quick and cheap to get the shafts epoxied in properly.