How to fix "Invalid page redirect" with links containing plus signs (+)?

Question

Nginx

Salute comrades!
There is a fresh install of MediaWiki with plugins enabled by default.
The wiki itself lies in the DocumentRoot, in a virtual machine with Apache installed (not configured). Behind the virtual machine is Nginx with the following rule

server {
        listen 80;
        server_name mysite.net;
        proxy_set_header Host $host;

        location / {
                return 403;
        }

        location /mwiki/ {
                proxy_pass http://172.16.18.50/mwiki/;
                proxy_set_header   Host             $host;
                proxy_set_header  X-Forwarded-For  $proxy_add_x_forwarded_for;
                proxy_redirect default;
        }

And everything works fine, except for the articles ala "Test + non-test". In the browser the string is replaced with
http://mysite.net/mwiki/index.php/Тест_%2B_нетест
but the browser throws an error (Firefox)

Wrong page redirect

On the old configuration, this worked fine, but unfortunately, that instance has sunk.
Tell me what I'm doing wrong