It seems I have figured out the issue. It was directly related to the SEO friendly URL. I think it was a combination of a few things I did. I will just leave my solution for future guests.
- Since we use multi-store, I put it on the default store (not to be confused with default group)
- Under the “SEO & URLs” section, I enabled friendly URL's
- In that same section, I modified the “module-realexpaymentshpp-validation” custom URL.
- Saved it
- I also reconnected other modules that were previously not working while in “friendly URL” mode by clicking the “add” button at the top and entering a custom URL.