During my second run-through of Syrcus Tower, when we reached the Amon boss it became bugged and none of the mechanics in the fight happened. Everyone literally attacked him from 100%-0 with no additional enemies spawning, no special moves being cast, as far as I could tell he was just auto-attacking the tank, possibly not even that. There were no mechanics to contend with and it was essentially a free win.

The Summoner in my party also reported that during this fight his DoT skills weren't functioning correctly, only lasting 1 second on application.

I don't know if it's a cause, but the boss was pulled by another Summoner's Garuda-Egi, before being provoked away.