I played a solo Challenge Underground 1 phase mission, no directives, against LMB. Played through several rooms and noticed I was not hearing when enemies were killed (no screams, groans, or chatter). I noticed there wasn't any typical NPC chatter, and then suddenly I hear all the death noises and chatter at once, very delayed.
https://youtu.be/LiBQiBIrD2g?t=2m20s
Hey, this has been passed on to the team already but I will update with the video you provided.
/gabelikes