Adding a Custom Location takes the Site offline

Are you in the right place?

• Yes

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
• If having problems with Lets Encrypt, have you made absolutely sure your site is accessible from outside of your network? Yes

Describe the bug

• I have a very simple Site setup, which proxies to a quasar app (Works). The only thing I have enabled (though I tried all settings) is to force ssl
• Now everything works fine. I can reach my site under the domain name. SSL is enabled, http requests get redirected to https
• Now I edit the Proxy Host and add a custom location /api
• Upon Saving my changes the site is taken offline

To Reproduce
Steps to reproduce the behavior:

1. Create a Simple Proxy Host with SSL (Lets Encrypt Enabled)
2. After Certificate is setup make sure the site is reachable
3. Now Edit the proxy host and add a simple Custom location (/api)
4. Site is taken offline

Expected behavior
The Site stays online and is reachable. The /api Url is also reachable

Operating System

• Current Debian as Docker host

Additional context
Basically I am trying to host a modern SPA Website. The Frontend is created using quasar/vue 3 and the Backend, which is a simple rest api is done using Dotnet Core C#. I want to host the quasar App under / and the api under /api.

Start by reproducing the issue using the listed Proxy Host, SSL, and /api Custom Location steps on the Docker setup described. The issue names no source files or tests, so inspect the generated proxy configuration and the failure behavior after saving. Done means the existing site remains reachable and /api is reachable as well.