I've noticed the stuttering doesn't happen at the First and Second Circle of the new raids for me. It comes back at the Third Circle and becomes unbearable at the Fourth.

Also, it's probably not related to this issue, but in System Configuration > Sound Settings there's an option called "Play sounds when window is not active". I only have it set to play System Sounds and yet, when duty queue pops I can hear the game's BGM with every "tick" sound the queue window does, as if both types of sounds were integrated to each other. This didn't happen before 6.0.