Cant discard duplicate Artifact set

I did the quests for jobs in which I already had Artifact Sets and I got another set of those pieces, now I am stucked with two same pieces of the same armor just taking space in my inventory and I cant sell or discard the extra one I have. What can I do to solve this?

Hope anyone can help me with this

There are about 10000000 threads with the same issue. They're working on it but have not fixed it yet. Any item in your retainer / etc doesn't count as you having it. So you can accidentally get multiple of the gear.