To view the original post, please click hereI have confirmed this issue and submitted a problem report into the system on the matter.This is a quest item obtainable in the shimmering effusion room, if you pick it up and you have already done the quest it stucks in the backpack until a GM don't remove it manually.
Since this item gives a "large bag of treasures" as reward could be a good fix to remove the quest limit of 1 time per character so everyone can get rid of it by completing the quest instead of calling the GM.