Just in general, it’s really important to determine if the Chinese clients are going through a VPN for Discourse and everything else internally or if they’re just accessing as a secure site over the wider internet. You may consider routing them through a VPN if they aren’t or using some other technology to proxy/ensure the connection isn’t being mangled outbound.
You should also try routing your non-Chinese workers through any VPN tools the Chinese users are using, to see if it’s an issue caused by VPN software or proxying connections weirdly.