WordPress multisite second site admin resulting in too many redirects error

Question

I have a multisite installation that seems to be working just fine for the first site, but for the second site, the admin panel results in a "too many redirects" loop. What is the correct nginx or wordpress configuration to get this to work?

I have a non-WordPress installation at example.com
My first blog is setup at example.com/blog
My second blog is setup to be example.com/blog/tr. The frontend renders just fine.

The admin for the first site works just fine, as does the network admin panel. So https://example.com/blog/wp-admin and https://example.com/blog/wp-admin/network/ result in pages that work fine. The url https://example.com/blog/tr/wp-admin results in too many redirects, though.

My nginx configuration for the wp-admin sections looks like this

if (!-e $request_filename) {
     rewrite /wp-admin$ $scheme://$host$uri/ permanent;     
     rewrite /wp-admin$ $host/$uri/ permanent;
     rewrite ^(/[^/]+)?(/wp-.*) $2 last;
     rewrite ^(/[^/]+)?(/.*.php) $2 last;
}

Here are my wp_blogs and wp_site tables

mysql> SELECT * FROM wp_site;
+----+-------------+--------+
| id | domain      | path   |
+----+-------------+--------+
|  1 | example.com | /blog/ |
+----+-------------+--------+

mysql> SELECT blog_id, site_id, domain, path FROM wp_blogs;
+---------+---------+-------------+-----------+
| blog_id | site_id | domain      | path      |
+---------+---------+-------------+-----------+
|       1 |       1 | example.com | /blog/    |
|       2 |       1 | example.com | /blog/tr/ |
+---------+---------+-------------+-----------+

wp-config.php

define( 'MULTISITE', true );
define( 'SUBDOMAIN_INSTALL', false );
define( 'DOMAIN_CURRENT_SITE', 'example.com' );
define( 'PATH_CURRENT_SITE', '/blog/' );
define( 'SITE_ID_CURRENT_SITE', 1 );
define( 'BLOG_ID_CURRENT_SITE', 1 );

I've tried changing the path for the second blog, to something with a different path like /blg/tr in case it was a path collision error, and I was still getting the problem. I also tried creating a second site in wp_sites and associating the second blog with that second site, also didn't do anything different.

I also put in specific nginx location blocks for specifically /blog/tr/wp-admin and that seemed to break it more in different ways.

Is there anything I am missing or additional documentation that I am not finding to help debug my second site's wp-admin section?

Reviewed documentation / suggested steps:
https://wordpress.org/support/article/debugging-a-wordpress-network/
https://www.wpbeginner.com/wp-tutorials/how-to-install-and-setup-wordpress-multisite-network
https://gist.github.com/JustThomas/141ebe0764d43188d4f2
Trying to access second site dashboard on a multisite configuration proceeds to an error
https://docs.bitnami.com/aws/how-to/troubleshoot-wordpress-issues/

EDIT: Full nginx config

server {
        listen 80;
        listen 443 ssl;
        ## Your website name goes here.
        server_name example.com;
        ## Your only path reference.
        root /Users/lfarr/Sites/blog;
        ## This should be in your http block and if it is, it's not needed here.
        index index.php;

        ssl_certificate     /usr/local/etc/nginx/ssl/example.com+4.pem;
        ssl_certificate_key /usr/local/etc/nginx/ssl/example.com+4-key.pem;

        location = /favicon.ico {
                log_not_found off;
                access_log off;
        }

        location = /robots.txt {
                allow all;
                log_not_found off;
                access_log off;
        }

        if (!-e $request_filename) {
            rewrite /wp-admin$ $scheme://$host$uri/ permanent;
            rewrite /wp-admin$ $host/$uri/ permanent;
            rewrite ^(/[^/]+)?(/wp-.*) $2 last;
            rewrite ^(/[^/]+)?(/.*.php) $2 last;
        }

        #avoid php readfile()
        location ^~ /blogs.dir {
            internal;
            alias /var/www/example.com/htdocs/wp-content/blogs.dir ;
            access_log off;     log_not_found off; expires max;
        }

        location / {
                # This is cool because no php is touched for static content.
                # include the "?$args" part so non-default permalinks doesn't break when using query string
                try_files $uri $uri/ /index.php?$args;
        }

        location ~ \.php$ {
                #NOTE: You should have "cgi.fix_pathinfo = 0;" in php.ini
                include fastcgi_params;
                fastcgi_intercept_errors on;
                fastcgi_pass fastcgi_backend;
                #The following parameter can be also included in fastcgi_params file
                fastcgi_param  SCRIPT_FILENAME $document_root$fastcgi_script_name;
        }

        location ~* \.(js|css|png|jpg|jpeg|gif|ico)$ {
                expires max;
                log_not_found off;
        }
}

Answer 1

There seems to be some issue the the nginx config. Is there any reason you have modified this rule differently then as documented in the wordpress documentation ? (https://wordpress.org/support/article/nginx/#wordpress-multisite-subdirectory-rules)

I am specifically talking about following rule :

if (!-e $request_filename) {
 rewrite /wp-admin$ $scheme://$host$uri/ permanent;     
 rewrite /wp-admin$ $host/$uri/ permanent;
 rewrite ^(/[^/]+)?(/wp-.*) $2 last;
 rewrite ^(/[^/]+)?(/.*.php) $2 last; 
}

I think you can remove the 3rd line in the above rule ( rewrite /wp-admin$ $host/$uri/ permanent; ) as it's not there in the documentation too .. and I think all needed is already there in the first rule of this block.

Beside that in the last rule (rewrite ^(/[^/]+)?(/.*.php) $2 last;) is missing an escape sequence, which is also present in the documentation. So Can you try replacing the above block completely as present in the document like shown below ?

if (!-e $request_filename) {
        rewrite /wp-admin$ $scheme://$host$request_uri/ permanent;
        rewrite ^(/[^/]+)?(/wp-.*) $2 last;
        rewrite ^(/[^/]+)?(/.*\.php) $2 last;
    }