Can't place Grip of Kulemak unique ring into it's unique item stash tab slot

I bought a Grip of Kulemak unique ring but it won't allow me to place it in the Unique Stash Tab. I've tried using the normal hotkeys, even manually dropping it in the tab and it won't move the item. I can move it to other generic stash tabs just fine, and I can move other unique items into that unique stash tab. I can see in the Unique Stash Tab that there is a slot for Grip of Kulemak, as it does show a ??? slot when I do a keyword search for "Grip of Kulemak" in the tab. So I'm not sure what's preventing it from being placed there.

+1, there is a spot for it but it will not accept it