Here's a screen cap and error message for an item that isn't displaying. Hope it helps.
Went to equip it, and it spawned duplicates in my inventory: 
Naturally, my first thought was to abuse the hell out of this to spawn a bunch to sell. Mousing over one of the later duplicates produced a very dense error message which might help point you toward the bug: 
And here I am abusing the exploit to become the richest man on Axu. Didn't even need to go out of the equip menu to spawn them. Each time I'd hit enter on equip one would spawn without taking me out of the menu.