I had a lvl 8 ring with a slot. It was a ring I got from my first character play through and put in my chest to use if I started another class.
So when I decided to pull it out i thought why not toss in a gem while i was at it since it had an empty slot. I had several gems all different qualities. I didnt pay attention that the normal (diamond shaped) emerald I had was only for lvl 40. I tossed it in and that was when a lock appeared on the ring. I decided when I was high enough to pull it out, and if the ring was still better than what I had or could fine by the time I turned lvl 20, I would remove gem and shouldnt have an issue with wearing it. Sadly it didnt work out that way.
I reached lvl 20 and was able to finally remove the Normal Emerald from my ring. it came out but my lvl 8 ring is now perm lvl 40. Which is terrible because its stats are for lvl 8 yet it is now perm set to be worn for lvl 40. Now a decent ring for me is now trash because I can not even use it. By lvl 40 it is trash. So def a terrible bug.