Web resources transferred with the wrong MIME type

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, this is the docker compose
• Have you searched for similar issues (both open and closed)?
  • Yes, found this similar one: #284

Describe the bug
When accessing a proxied server, the browser blocks some resources because of a wrong MIME type

Nginx Proxy Manager Version
v2.9.19

To Reproduce
Steps to reproduce the behavior:
Perhaps it's an issue with custom locations:

1. Access server like hostip/service
2. inspect
3. open console
   There may be errors loading some resources

Expected behavior

Screenshots
Console error

nextcloud, like this because it doesn't load css
homeassistant, stuck here because it doesn't load js

setup screenshots:
NPM, proxy host
and custom locations

Operating System
Raspberry pi (192.168.1.5) with raspberry OS and all the services are on docker, on the same bridge network: NPM (172.19.0.4), portainer (172.19.0.3), nextcloud (172.19.0.5) and homeassistant (172.19.0.2) of which NPM and portainer properly load, while nextcloud and homeassistant fail to load some resources

Additional context
Have tried with firefox and chrome. Accessing directly works fine.
NPM logs are clear, there is the browser request and the file is sent

Logs for a connection to NPM and then portainer
proxy-host-6_access.log
proxy-host-6_error.log

Logs for connections to nextcloud and then homeassistant
proxy-host-6_access.log
proxy-host-6_error.log

Start by reproducing the issue with the linked docker-compose configuration and compare direct versus proxied requests for Nextcloud and Home Assistant. Use the browser console and the attached proxy access and error logs to trace the affected CSS and JavaScript resources. Done means those resources load through the custom-location proxy with the correct MIME type.