Plantronics + Polycom.
Now together as
I am using m100 in my Beijing office in China and dialing into a gatekeeper in a state school network in Australia.
The Australian gatekeeper can hear and see the China m100 person perfectly, but the China person can barely hear and see the Australian gatekeeper very well.
The m100 says there is close to 50% packet loss.
The Australian gatekeeper does many video calls within their network. I don't think the issue is at the Australia network end.
Possible not enough bandwidth in China, or the network is half-duplex. That would be the first places to look.