From what MR support staff told me they are using private proxy for dynamic ip. Hence got problems with access to china websites.
Which BTW why MR do not use public proxy for easier access to china websites?
Maybe because MR is the only ISP that doesn't give their users a true PUBLIC dynamic IP address.
Theirs is a NAT network, using only private ip addresses which have a number of limitations that other ISP recognized and avoids.
Or maybe their staff are using the terms 'proxy' and 'NAT' interchangeably. Anyhow they've confirmed its their NAT/Proxy limitation.