WebDAV MOVE Fails: NPM Auto-Added Host Header Overrides Custom Config

Checklist

• Have you pulled and found the error with jc21/nginx-proxy-manager:latest docker image?
  • Yes
• Are you sure you're not using someone else's docker image?
  • Yes
• Have you searched for similar issues (both open and closed)?
  • Yes

Describe the bug

When configuring a Custom Location / with custom proxy_set_header directives, NPM automatically adds proxy_set_header Host $host; which overrides the intended custom setting. This causes issues with services that require the full Host: hostname:port format (e.g., WebDAV services).

Specifically, when adding proxy_set_header Host $http_host; in Custom Location config, NPM still injects proxy_set_header Host $host; after it, making the custom setting ineffective.

To Reproduce

1. Create a proxy host pointing to a backend service
2. Add a Custom Location with path /
3. In the custom Nginx configuration, add: proxy_set_header Host $http_host;
4. Save and reload
5. Check the generated Nginx config file - proxy_set_header Host $host; still exists and overrides the custom setting

Expected behavior

Either:

• The custom proxy_set_header Host directive should not be overridden by auto-generated defaults
• NPM should detect duplicate directives and use the custom one instead
• NPM should provide an option to disable auto-injection of certain headers

Operating System

Docker (jc21/nginx-proxy-manager:latest)

Start by inspecting the generated Nginx configuration for a Custom Location and trace where the automatic proxy_set_header Host $host; directive is added. Reproduce the configuration with proxy_set_header Host $http_host;, then verify that the custom directive is no longer overridden and the configuration still reloads successfully.