Lately, when you upgrade a gear it disappears, but only momentarily. If you go up to diff hero, then back it's back to the upgraded one. That is just a visual lag issue I suppose. But it can throw ya off. Just mentioning, didn't used to do that.
and sometimes instead of disappearing the old level with the arrow is still there and if you click on it and then click on the material you end up with material that you may not need because you already upgraded.
The opinions expressed on this post are my own as a player, not as a Moderator.