WordPress Publishing Error

Problem

Recently while working on a WordPress project , I encountered a weird error where I wasn't able to update or publish a simple post in my local WP admin.

Solution

Since the error message had to do with a JSON response, I initially thought it was a Gutenberg or ACF issue. But it turned out this was happening because I was on the https WP admin

It was a CORS error!! I was trying to modify a non-https domain from a https domain. Switching to a non-https WP admin allowed me to publish posts with no problem.