Hello there. First time poster. I recently got this game and am loving it! I was playing multiplayer mode with 1 other person and ran into this bug. (My friend was the host and I was the guest of the game.)
We found a magical item which was sent to my wizard. He used ritual identify to discover what it was and sent it back to the other person. I was looking at the other person's inventory of the item when they sent it back to my character. It was in both my inventory and theirs. Then, when I sent it back, they had 2 and I had 1. I eventually equipped it and attuned to it. While attuning, it took up 3 slots since there were 3 of the same exact item, so now I don't have additional slots for other magical items. My friend only saw 1 item the entire time.
I only took a screenshot of the item appearing twice in my bag, but I've attached it here. Other than this bug, I'm enjoying the game and haven't run into anything else! <3