Creating an API proxy using HAProxy and getting responses - haproxy

Question

I have an issue where an API vendor requires a static IP to connect to it and I do not have the ability to configure a static IP for the requests, so I am looking at using HAProxy as my gateway/proxy to the API.
It was very easy to configure HAProxy in a basic form and have it proxy my requests, but I'm finding that some requests return no response while others do.
The API requests will use PUT, POST and GET methods. My config is very similar to default. I'm using HAProxy 1.8.
Two questions;
Is HAProxy the right tool for this? Will anything else work? I'm even happy to pay for a commercial tool that does the job.
If it is the right tool, is there any reason why some GET requests return responses and some dont? The response code is still 200 but I have no access to logs on the API vendor side to troubleshoot.
#---------------------------------------------------------------------
# Example configuration for a possible web application. See the
# full configuration options online.
#
# http://haproxy.1wt.eu/download/1.4/doc/configuration.txt
#
#---------------------------------------------------------------------
#---------------------------------------------------------------------
# Global settings
#---------------------------------------------------------------------
global
# to have these messages end up in /var/log/haproxy.log you will
# need to:
#
# 1) configure syslog to accept network log events. This is done
# by adding the '-r' option to the SYSLOGD_OPTIONS in
# /etc/sysconfig/syslog
#
# 2) configure local2 events to go to the /var/log/haproxy.log
# file. A line like the following can be added to
# /etc/sysconfig/syslog
#
# local2.* /var/log/haproxy.log
#
#log 127.0.0.1 local2
log 127.0.0.1:514 local0
chroot /var/lib/haproxy
pidfile /var/run/haproxy.pid
maxconn 4000
user haproxy
group haproxy
daemon
# turn on stats unix socket
stats socket /var/lib/haproxy/stats
#---------------------------------------------------------------------
# common defaults that all the 'listen' and 'backend' sections will
# use if not designated in their block
#---------------------------------------------------------------------
defaults
mode http
log global
option httplog
option dontlognull
option http-server-close
option forwardfor except 127.0.0.0/8
option redispatch
retries 3
timeout http-request 10s
timeout queue 1m
timeout connect 10s
timeout client 1m
timeout server 1m
timeout http-keep-alive 10s
timeout check 10s
maxconn 3000
log-format "%ci:%cp [%tr] %ft %b/%s %TR/%Tw/%Tc/%Tr/%Ta %ST %B %CC %CS %tsc %ac/%fc/%bc/%sc/%rc %sq/%bq %hr %hs %{+Q}r"
#---------------------------------------------------------------------
# main frontend which proxys to the backends
#---------------------------------------------------------------------
#frontend main *:5000
# acl url_static path_beg -i /static /images /javascript /stylesheets
# acl url_static path_end -i .jpg .gif .png .css .js
#
# use_backend static if url_static
# default_backend app
frontend api_proxy
bind *:6109
mode http
# capture response header
default_backend remote_api_server
backend remote_api_server
#replace 10.10.10.10 with the actual Ip address
mode http
http-request set-header Host myhost.com.au
server server1 myhost.com.au:443 ssl verify none
#---------------------------------------------------------------------
# static backend for serving up images, stylesheets and such
#---------------------------------------------------------------------
#backend static
# balance roundrobin
# server static 127.0.0.1:4331 check
#---------------------------------------------------------------------
# round robin balancing between the various backends
#---------------------------------------------------------------------
#backend app
# balance roundrobin
# server app1 127.0.0.1:5001 check
# server app2 127.0.0.1:5002 check
# server app3 127.0.0.1:5003 check
# server app4 127.0.0.1:5004 check

Answer 1

So, the use of HAProxy continued to not behave the way I expected so I tried doing what I needed in nginx and it was so easy.
Ultimately, this block does exactly what I need.
server {
listen 6109;
location / {
proxy_redirect off;
proxy_pass_header Server;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Scheme $scheme;
proxy_set_header Host myhost.com.au;
proxy_set_header X-NginX-Proxy true;
proxy_connect_timeout 5;
proxy_read_timeout 240;
proxy_intercept_errors on;
proxy_pass https://myhost.com.au:443;
}
}
This is on an EC2 instance so I have a load balancer in front of it handling SSL.