Hi, this is a minor inconvenience but the quest flags for certain items do not get removed upon quest completion, making them take up space in your inventory (some have weight as well) permanently. The items I've run into so far are Gallius' encoded journal and Attunement Sphere. It would also be nice if you could make quest items able to be deposited into the chests in any homes you own, as it's a tad annoying to carry around items like the Stones of Beneziah (which i probably will never find all 24 of). Thanks!

Also remembered the Amulet of Telos. If this is a quest item, why do I have 2? I cannot deposit either. (I'm only maybe 60-70% through main quest so I don't know if these flags get removed, but it doesn't seem like a quest item,)

Same for me, I am unable to drop the stones of Barenziah, the Ruby Dragon Claw, Rjorns Drum, the Sphere of Atunement, the Curious Silver Mold, the Elder SCroll, the Children of the Sky (Book), and King Olaf's Verse (book). All of them have weight.

I am able to remove and sell the amulet of Talos so i dont know what issue your having there sorry.

I think it has to do with the guy being executed at Solitude. He has one on him, and for whatever reason I am unable to drop either Amulet of Talos I have acquired (the other being loot from somewhere).