Final boss, for sure on HM, has a nasty habit of bugging out and during the shade phase one or more of the shades will not follow their target. We've had to impatiently wait for the shade to charge several times towards the trap to get out of the phase. It's a speed run/trifecta killer. I think recently it's happened each time we've been in there but this last time we had 2 shades get stuck, but sometimes it could be one shade per phase. Doesn't seem to matter where they are in the arena as we've found the stuck shades in different places.

I think this speaks to a bigger issue where this last patch I've noticed adds just don't move when in combat the way they should.