Guild Wars 2

So, this is the second time i’ve had this bug in a few months (it seems to be rather rare). Both times, it happened during a d/d elementalist fight, though this time i was only observing (pvp observer mode). After the ele used fire ring, the sound suddenly disappeared and was replaced by faint sound of a flame (which sounds kind of like the flame from fire ring). With the sound gone, the fps start to slowly drop over time, from 50fps at the start to 10fps in about half an hour (the drop is not linear, the first 10fps were gone quite fast and it constantly slowed down from there).

I recorded a short video about it:
https://www.youtube.com/watch?v=r1Y2EIXQj4U
Also note how the “The battle starts soon” message was still standing there, and got replaced by an also not disappearing “Svanir is back” message.
Maybe someone can make sense of this.