Cannot disable Proxy Mode and add "location /" to additional nginx directives simultaneously: nginx: [emerg] duplicate location

Symptoms

Cannot disable Proxy Mode and add nginx directive containing location / in Domains > example.com > Apache & nginx Settings simultaneously:

PLESK_ERROR: Invalid nginx configuration: nginx: [emerg] duplicate location "/" in /var/www/vhosts/system/example.com/conf/vhost_nginx.conf:1 nginx: configuration file /etc/nginx/nginx.conf test failed

Cause

This is a Plesk bug with ID PPPM-9841 which is planned to be fixed in future product updates.

Resolution

As a workaround until fix available:

1. Log into Plesk;

2. In Domains > example.com > Apache & nginx directives temporary remove additional nginx directive containing location /;

3. Disable Proxy Mode and click Apply;

4. Insert the necessary directive back into Additional nginx directives and click Apply;