Level 60 Class Treasure Coffers

I am having an issue opening the following coffers received after completing LV60 Class quests for Bard and Paladin:

Aoidis' Attire Coffer
Creed Armor Coffer

I am the proper classes and levels and have plenty of room in my inventory. The message I receive when trying to open them is as follows:

Unable to use the aoidos' attire coffer. You cannot carry more than one unique item of the same type.

Unable to use the creed armor coffer. You cannot carry more than one unique item of the same type.

I do not have any pieces of any of these coffers in any of my inventories. Has anyone had this problem?

Are you 100% sure that you dont have any of those items already? Specifically the belts?

You have your DRK and your Machinist up to level 60 after all - if you opend their treasure coffers aswell, you got Fabled Belts of Aiming/Fending and those are included on the Aoidis and Creed Coffers too (even though the rest of the gear is unique).

I think you can get some of those pieces randomly from ventures too, although I'm not 100%. Might just be the level 50 ones?