Experience:
Someone in your group isn't heard by others in the group, even when in range, but you can hear sounds from that person's background, such as gear noise, equipment noise, etc.
Possible causes and remedies:
This may be due to how that person's Milo is mounted. For example, the Milo microphones are not positioned close to their mouth, so the voice activation detection (VAD) function doesn't easily activate. Instead, the VAD is keying off surrounding noises that are louder than the person's voice, thereby transmitting noises rather speech to the group.
Reposition Milo such that it more easily can pick up the person's voice. Check out Best Mounting Options for Milo placement ideas.