Another bug that has been around for as long as I can remember.
On the first boss in AA, often the light circles don't show up. Usually they will be visible for at least a few people in the group, so someone makes the call and we make it through OK. But occasionally no one can see the lighted circle, and we end up losing vitality which forces us to restart the Trial.
I'm not sure I've ever run this Trial where I saw every light circle during the lightning phase.
It's pretty frustrating and ruins a lot of good runs.