10.5 server proxy setup

I have an erp http service running on unsecured port 8080 on my main server. I would like to use reverse proxy to proxy https://servername/erp to http://servername:8080

I can setup reverse proxy in both the serveradmin gui or directly in the /etc/apache2/sites/0000_any_443….. conf file at the root i.e. https://servername and it redirects fine. However, if I try to redirect servername/erp I get problems with only some of the content being served. Are there any special tips for setting up reverse proxy?