Http and https Mixed Content issues with forms (Partially resolved with HAProxy)

Hello All,

Currently I have issues with mixed content on one of the site I am testing and trying to resolve it. To resolve mixed content I was able to add the following to HAProxy in PFSense:

Modifying Header in PFSense (Firewall) in HAProxy Backend (Best Method so far I found)
Header always set Content-Security-Policy: upgrade-insecure-requests

by doing so I am able to resolve most http to https and solve mixed content issues for images, links, etc. but it seem like the forms I have still have the following mixed content issues I think. Site is showing secure at least.

The best solution is to fix the app behind HAProxy that is serving the mixed content.