It's not just a regular echo (oh no, it's a special echo), the sound being picked up is being echoed as clearly when the actual person said something. It's actually clearer and louder than Mil, so that we can't hear what he's saying behind it.
I'm sure others have had this problem (and don't now) and hoped we knew what fixed the problem. The only thing I knew to do was to mute microphone. =\