Terrible feedback on Turtle Beach Stealth 600

My friend and I both have the Stealth 600 headset, and when we are in party chat, if anyone speaks at a slightly loud speaking volume, a feedback loop will start... turning into a loud repeating chirp. Once the chirp starts, one of us has to mute until it stops.

We have dropped our mic monitoring, checked firmware on controllers console and headset, but problem persists... any ideas?