This bug has been in-game since the April 14th patch, but I haven’t seen anyone report it yet and since it wasn’t fixed in this week’s patch either it’s possible it isn’t even known about yet.
At the Triple Trouble event, both the Amber and Cobalt wurms have no audio for any of their animations. Interestingly, the Crimson wurm still has its audio on normally. For those of us relying on audio cues to dodge the spins for example this is an annoying bug.