Issue with Mastodon installed via source

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

I installed Mastodon from source and configured it to be on port 3000. I have gotten it to at least partially work, however under advanced I'm unable to add these lines:

proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";

when I do, NPM removes the existing conf file, and replaces it with nothing.

Nginx Proxy Manager Version

v2.12.3 © 2024

To Reproduce
Steps to reproduce the behavior:

1. Add New Proxy Host
2. Turn on Websockets Support
3. Add SSL
4. Add a Custom Location (e.g., for /api/v1/streaming, pointing to your streaming server details).
5. Go to the Advanced tab of this specific Custom Location (e.g., for /api/v1/streaming).
   Add the lines:

proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";

6. Click 'Save' for the Proxy Host.
   Expected behavior

It should work like it does in the default nginx

Screenshots

[6/17/2025] [4:22:27 AM] [Nginx ] › ⬤ debug Deleting file: /data/nginx/proxy_host/4.conf
[6/17/2025] [4:22:27 AM] [Nginx ] › ⬤ debug Could not delete file: {
"errno": -2,
"code": "ENOENT",
"syscall": "unlink",
"path": "/data/nginx/proxy_host/4.conf"
}
[6/17/2025] [4:22:27 AM] [Nginx ] › ℹ info Reloading Nginx
[6/17/2025] [4:22:27 AM] [Global ] › ⬤ debug CMD: /usr/sbin/nginx -s reload

Operating System

Ubuntu 22.04.5 LTS
Docker version 28.2.2, build e6534b4
Mastodon v4.3.8

Additional context

Did also find that this error presented by erasing and then not replacing the conf file in nginx-proxy-manager/data/nginx/proxy_host till the lines were removed.

Reproduce the proxy-host and custom-location steps with Mastodon on port 3000, then inspect the generated /data/nginx/proxy_host/4.conf and the deletion/reload logs. Trace how the Advanced-tab directives are processed and persisted; done means the directives remain in the generated configuration and Nginx reloads successfully.