Weird Annoying Bug/glitch

While doing legendary island, I really enjoy fighting each boss and have been having lots of fun but for some reason a bug has been going on. Me using a super fast attack speed build usually attacks the enemy by spam clicking. When I kill a boss that has different stages, sometimes the boss spawns twice when it goes into it's 2nd stage spawning two bosses in. I don't know if anyone else has gotten this but this has only happened recently on my times on wynn, mostly in legendary island.

 

Try to avoid hitting them right at the moment they die.
As for the bug, hopefully it'll be fixed, soon.