It's an unusual wear, you could try and speak to the shop you brought them from, but with over 2,000 miles, it's not unusual for tyres to come unbonded from the carcass.
I've spoken to sigmasport on Twitter and they've suggested I email them so I'll see if anything comes of it. I was replacing them anyway so I'm not too fussed...
It's an unusual wear, you could try and speak to the shop you brought them from, but with over 2,000 miles, it's not unusual for tyres to come unbonded from the carcass.