Hello:
I have a character who cannot equip a set item that upgrades from normal to exceptional, I meet all the stat and level requirements to equip it, this item can be equipped by other characters in other runs, but neither the mercenary nor the main You can, as a curiosity, I sold this object and repurchased it to see if anything changed and when I tried to buy it it told me that I had no space when my inventory was empty, I was able to buy it by clicking a lot, additionally, my game is local and something had never happened to me So, I suppose that the object was bugged when applying the upgrade, please give your support to review the issue since I hope it is not a problem that affects only ones or other sets as well.
Greetings