Problem with SubFolder install

I have your plugin working correctly on a SubFolder network with the main site accessible at https://127.0.0.1 and the translation at https://127.0.0.1/es

Now I need to move it into a folder with the main site at https://127.0.0.1/mysite and the translation at https://127.0.0.1/mysite/es. Should that be possible?

Translations are linked correctly, but the main site https://127.0.0.1/mysite/es and all subpages do load with a lot of 404 as referenced files (like https://127.0.0.1/mysite/es/wp-includes/js/jquery/jquery-migrate.min.js?ver=3.4.1) can’t be found).

Here are the files and database tables I changed (in bold) in order to get it working, but without the described problems:

wp-config.php:

/* Multisite */
define( 'MULTISITE', true );
define( 'SUBDOMAIN_INSTALL', false );
define( 'DOMAIN_CURRENT_SITE', '127.0.0.1' );
define( 'PATH_CURRENT_SITE', '/mysite/' );
define( 'SITE_ID_CURRENT_SITE', 1 );
define( 'BLOG_ID_CURRENT_SITE', 1 );

.htaccess:

RewriteEngine On
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]

wp_site:

domain	path
https://127.0.0.1	/mysite/

wp_sitemeta:

site_id	metakey	metavalue
1 		siteurl	https://127.0.0.1/mysite/

wp_blogs:

blog_id	site_id	domain	path
1	1	127.0.0.1	/mysite/
4	1	127.0.0.1	/mysite/es/

wp_options:

option_name	option_value
siteurl	https://127.0.0.1/mysite
home	https://127.0.0.1/mysite

wp_4_options:

option_name	option_value
siteurl	https://127.0.0.1/mysite/es
home	https://127.0.0.1/mysite/es