Had to disband Earth 3: The Panopticon due to invulnerable Security Bots. We tried to damage them by blocking, but it was taking too long, so the group became impatient. This has been happening a lot more since I returned last year than I recall in 2013-2017. I remember it happening some back then and there even being a thread a developer created to report it back then, but it's bad now.
I've noticed it at least twice. I don't remember the events specifically, just that a mob went invulnerable. I know for sure one was a drone of some sort, but I don't think it was Panopticon. Once it was pulled away and went back to its spot it was vulnerable again though.
We usually remove our gear, wipe, and everyone wait at rally point. Usually works 90% of the time, but 1 in 10 we will have to disband.
Yeah, Wonderverse had 2 points where this would happen. Right before Grail and right before the final staircase. Not a lot of rhyme or reason as to when it would happen. Sometimes you couldn't wipe though as you were out of combat and the adds were not really responsive. Youl could have everyone leave and get invited back in to cycle the room, but again, that was no guarantee that it would be fixed as a result. Sometimes, there are certain powers that will do damage still. Not sure what the difference is, but I know mental had a power (cryogenesis?) that seemed to do damage to the invulnerable adds.