Pettas Vera appears invisible during Urgent Quests. I can see other players' damage numbers, and even the effect when the boss gets stunned, but I cannot damage nor collide with the boss, and it can't seem to damage me either. I still receive the full rewards when the other players clear the UQ, however I don't get the option to leave. In fact I can't even open any menus—including chat—once the UQ finishes, I'm stuck in the area until I exit and relaunch the game.
This has happened to me on two separate occasions thus far. I rarely enter UQs apart from the weekly quest, so I don't know if this happens every time, or if it's random. I'll do some testing if I get the chance.