Spectre Minions Wisp Bug

There is a bug, where the spectre minions stay in a, let´s say "wisps form", without turning back to normal. I as a Player need to pass through those wisps, to bring them back. This happens during boss fights very often, for example at the Rotten Druid or Tor Gul (also during mapping and so on). I guess it happens because the spectre minions are to far away from me at a certain point during fighting and they try to catch up to me, because during that, they turn into that wisp ball and it seems they get stuck in it.
I also noticed that minions and spectre minions get excluded from some boss arenas like Zalmarath the colossus and crowbell (in the last fighting area, the mud pit).