Please correct /app/templates/_location.conf

/app/templates/_location.conf

Now you have:

{{ advanced_config }}

proxy_set_header Host $host;
proxy_set_header X-Forwarded-Scheme $scheme;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header X-Real-IP $remote_addr;

proxy_pass {{ forward_scheme }}://{{ forward_host }}:{{ forward_port }}{{ forward_path }};

please change the order => 1st your config, then the user's config. like this:

proxy_set_header Host $host;
proxy_set_header X-Forwarded-Scheme $scheme;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header X-Real-IP $remote_addr;

proxy_pass {{ forward_scheme }}://{{ forward_host }}:{{ forward_port }}{{ forward_path }};

{{ advanced_config }}

Otherwise your configuration overwrites the user configuration, which is not good :)

Start with /app/templates/_location.conf and inspect how the advanced_config block is placed relative to the proxy directives. Verify the rendered location configuration preserves the requested ordering, with the template's proxy settings before the user's advanced configuration. Done when the generated configuration reflects that order without unrelated changes.