NGINX Reverse Proxy (Proxy Manager) to OpenResty (NGINX) API Issues - nginx

Question

I am hosting an application (Tandoor) on a LXC container.
On my host I have another container with a NginxProxyManager installed.
The Proxy Manager forwards (and forces SSL) to all incoming connections to the correct container, this works perfectly for all my other applications.
I am really struggling to understand why Tandoor will not work.
My config on the Reverse Proxy:
location /authelia {
internal;
set $upstream_authelia http://10.10.10.4:9091/api/verify;
proxy_pass_request_body off;
proxy_pass $upstream_authelia;
proxy_set_header Content-Length "";
# Timeout if the real server is dead
proxy_next_upstream error timeout invalid_header http_500 http_502 http_503;
client_body_buffer_size 128k;
proxy_set_header Host $http_host;
proxy_set_header X-Original-URL $scheme://$http_host$request_uri;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Forwarded-Host $http_host;
proxy_set_header X-Forwarded-Uri $request_uri;
proxy_set_header X-Forwarded-Ssl on;
proxy_redirect http:// $scheme://;
proxy_http_version 1.1;
proxy_set_header Connection "";
proxy_cache_bypass $cookie_session;
proxy_no_cache $cookie_session;
proxy_buffers 4 32k;
send_timeout 5m;
proxy_read_timeout 240;
proxy_send_timeout 240;
proxy_connect_timeout 240;
}
location / {
set $upstream_app $forward_scheme://$server:$port;
proxy_pass $upstream_app;
auth_request /authelia;
auth_request_set $target_url $scheme://$http_host$request_uri;
auth_request_set $user $upstream_http_remote_user;
auth_request_set $groups $upstream_http_remote_groups;
proxy_set_header Remote-User $user;
proxy_set_header Remote-Groups $groups;
error_page 401 =302 https://auth.named-lab.net/?rd=$target_url;
client_body_buffer_size 128k;
proxy_next_upstream error timeout invalid_header http_500 http_502 http_503;
send_timeout 5m;
proxy_read_timeout 360;
proxy_send_timeout 360;
proxy_connect_timeout 360;
proxy_set_header Host $http_host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Forwarded-Host $http_host;
proxy_set_header X-Forwarded-Uri $request_uri;
proxy_set_header Access-Control-Allow-Origin *;
proxy_set_header X-Forwarded-Ssl on;
proxy_redirect http:// $scheme://;
proxy_http_version 1.1;
proxy_set_header Connection "";
proxy_cache_bypass $cookie_session;
proxy_no_cache $cookie_session;
proxy_buffers 64 256k;
set_real_ip_from 192.168.4.0/16;
real_ip_header X-Forwarded-For;
real_ip_recursive on;
}
location /accounts/logout/ {
return 301 https://auth.named-lab.net/logout;
}
My config on the OperResty (Tandoor) server:
server {
server_name tandoor.named-lab.net;
listen 8002;
#access_log /var/log/nginx/access.log;
#error_log /var/log/nginx/error.log;
#add_header Content-Security-Policy "default-src 'self';";
#add_header 'Access-Control-Allow-Origin' '*';
#proxy_set_header 'Content-Security-Policy' 'upgrade-insecure-requests';
#proxy_set_header 'Access-Control-Allow-Origin' '*';
#proxy_set_header Content-Security-Policy "default-src 'self';";
# serve media files
location /static {
alias /var/www/recipes/staticfiles;
}
location /media {
alias /var/www/recipes/mediafiles;
}
location / {
proxy_set_header Host $http_host;
proxy_set_header X-Forwarded-Host $http_host;
proxy_pass http://unix:/home/recipes/recipes.sock;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header 'Content-Security-Policy' "default-src 'self';";
proxy_set_header 'Content-Security-Policy' 'upgrade-insecure-requests';
}
}
I can see the interface load fine, and the auth system works great too. However as soon as I do anything that involves the API (https://tandoor.named-lab.net/api/*) the data doesn't load.
If I got directly to https://tandoor.named-lab.net//api/ the JSON data shows without issue...