That's interesting. Maybe I can test it.

Does this actually only affect Chinese Wikipedia? Have you tried another site?

I was able to edit from the UK (https://zh.wikipedia.org/w/index.php?title=%E9%95%BF%E6%B1%9F%E6%A1%A5%E9%9A%A7%E5%88%97%E8%A1%A8&type=revision&diff=66179551&oldid=66179546&diffmode=source / https://zh.wikipedia.org/wiki/User:RhinosF1/%E6%B2%99%E7%9B%92 )

Reproduced with adding an image to that article specifically. Request from <me> via cp3062 cp3062, Varnish XID 579161022
Error: 503, Backend fetch failed at Sun, 20 Jun 2021 13:44:25 GMT

The whole page seems very slow to load though

Can't be see on another article, see https://zhwp.org/w/index.php?title=%E8%A1%A8%E6%83%85%E5%8C%85&diff=66179631&oldid=65907999

Parser profiling data shows over 5 seconds to load it

To prevent me from messing with the Chinese Wikipedia, I tried to copy the article to my test page for testing…

The test showed that if I was doing an API edit to my mirror page in the sandbox, it would take the server for 6 seconds to process this edit, but no error would occur. Editing differences are attached: https://zhwp.org/w/index.php?title=User:Q28///&diff=prev&oldid=66180084

@IN: Please summarize outcomes when adding comments, and please avoid announcements-only. Every new comment creates notifications. Thanks.

In T285160#7164676, @Aklapper wrote:

@IN: Please summarize outcomes when adding comments, and please avoid announcements-only. Every new comment creates notifications. Thanks.

Oh, I'm sorry.