Unable to sell Dragon's Jade Hornbow Skin
When they changed the items from account-bound to sellable, it didn’t apply retroactively to those items that already existed, only to newly-created versions of the item. You had your item before the change, so it remained account-bound. This is pretty much the case with every change they make to items, apparently the system can’t change stuff that already exists when it comes to certain aspects of the items (like whether they’re account-bound or not).
If you buy one off the TP, or get another claim ticket and claim a new one, then stack the two together, both will become sellable. That’s the only real player-accessible solution to the issue.
Other than that, you could contact support. I’ve heard that some people have been able to get it fixed that way.
Thank you for your answer and it’s greatly appreciated.