Problems behind a reverse proxy

Application Version - OJS
PHP 7.2.24
Ubuntu 18.04.6
Apache2 2.4.29

I’ve been trying to run OJS behind a reverse proxy and failing. The base_url in is configured to be: base_url = and base_url[…] is also configured for index and my journal path. These are all correct. I have also been using mod_substitute in my proxy server and it looks like this:
This helps to get the rigth path for images and styles, but for some reason when submiting an article this happens:
For some reason this path won’t change no matter what I do

(Cross-posted: Error when submitting an article)