so, right after defeating the child of bones on an alt, I get this uncloseable window pop up "UI ERROR" with a bunch of indecipherable programming language, which from the part I understood seemed to be related to Player Level Progress Bar. Closing the game and relogging seemed to fix the problem (at least for now) but it's an annoyance nonetheless.
You can't see me. You can't see me. Neither can he. No one can see me.