In a new combat feature, you can hold right click and then left click a mob within a group to "swipe" across the group (using a sword).
This can result in multiple casualties at once, which AAC assumes to be Killaura, kicking the player.
AAC (our anti-cheat plugin) has fallen inactive as of recent and I fear it may not come back, as such we are running a beta version which contains bugs like this.
There is, however, another active (and premium) anti-cheat however, I don't want to purchase it only for AAC to return from the dead. I'm going to keep an eye on AAC and if it does not shown signs of returning, I'll remove it and replace it with AntiAura (the new anti-cheat).