Update: it is indeed soulbound, but I cannot figure out why. Is it the item’s property? Illusion? Component?
Update2: it was because of the illusion. Did not know illusions make items soulbound.
I’m not sure, but, in the early Xpac times, u had to remove the Illusion (=Illusion > Soulbound) to put it in the shared stash. Therefor it might be the same since then and u have to remove the Illusion first.