[gaoshan]

Many years back I was running a socks proxy for access while in China and I found that it worked great in Shanghai but was rapidly blocked (or degraded in some fashion) in Hangzhou. That seemed internal and not edge but I do no really know how they were interfering with it. Given Hangzhou's tech expertise it just may be the ISP there was more capable and up to date?

[kccqzy]

Was there an international event in Shanghai at that time? If they expected a large number of foreigners in a particular region they would relax the censorship in that particular region. They could even do it per hotel room where hotel rooms booked by foreigners automatically have lesser interference between GFW.

[gaoshan]

That might be it. I was there every year for about a 15 year period but this may have been around the time of the 2010 Expo. Though I was not in hotels, I was in apartments (ones owned and lived in by Chinese, not foreigners).