400 bad request, 403 forbidden error

Hi all,

So I recently edited my posts, and one of them turned up with this message in preview and the actual webpage:
Bad Request

Your browser sent a request that this server could not understand.
Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request.

the address of the webpage is as follows:
https://www.shenxin.info/episode-3-extras-%E7%AC%AC%E4%B8%89%E6%AE%B5-%E7%BE%A4%E4%BC%97%E6%BC%94%E5%91%98-2/

I tried emptying cache, and re edit the whole page over and over, and I don’t think it’s a problem of content. I’ve been trying to solve it for ages, and nothing worked so far. I’ve also contacted my domain support, and there’s nothing they could do about it.
I saw quite a lot of posts regarding this matter on the forum, anyone successfully solved this problem yet?

Thanks.