HAproxy -> HAproxy -> Collabora doesn't work

Hello, I have been having problems integrating Collabora Online with Nextcloud, the following happens I have the Collabora Online Server installed when I link it with Nextcloud, no problem, it sends me the legend Collabora Online server is recheable.

Currently I’ve following configuration to nextcloud:

HAProxy SSL → (inlets tunnel 8000 → 80) → HAProxy Http → Nextcloud server

The same configuration to Collabora:

HAProxy SSL → (inlets tunnel 8000 → 80) → HAProxy Http → Collabora server

So, I try with this configuration too:

HAProxy SSL → (inlets tunnel 8000 → 80) → HAProxy Http → Nginx Reverse Proxy (same server) → Collabora server

The problem is when I want to create a document or open a document with the odt extension is when it is stunned and practically blank, this could be because it is happening.

Doc

The config is following:

HA Proxy SSL

frontend http-in
            mode http
            bind *:80
            bind :443 ssl crt /etc/ssl/certs/web-certs.pem
            option httplog
            redirect scheme https if !{ ssl_fc }
            default_backend inlets

    backend inlets
            mode http
            stick-table type ip size 200k expire 30m
            stick on src
            server haproxy_tunnel 127.0.0.1:8000 check

HA Proxy Http

    frontend http-in
            mode http
            bind :80
            option httplog
            acl cloud hdr(host) -i cloud.server.org
            acl collabora hdr(host) -i collabora.server.org
            use_backend ha_nextcloud if cloud
            use_backend collabora_back if collabora

    backend ha_nextcloud
            mode http
            balance roundrobin
            stick-table type ip size 200k expire 30m
            stick on src
            server node1 10.1.1.29:80 check

    backend collabora_back
           timeout tunnel 3600s
           mode http
           server collabora_node1 10.1.1.12:9980 check