Can't equip more then 1 darkmantle set piece in BiS Tab

When trying to add darkmantle items to my gear in the BiS Tab i get the error -
Item Conflict
You can only equip one item from quest Dungeon Set 2.
i searched the forum but found no answer to this problem.

I bump bump bump bump bump.

This is still on my list of things to investigate – had a few server updates that required us to delay any other site updates last week.