I originally posted this in the Questions and Answers forum but received no reply there.
This is the issue:
I needed to add author details to a news items content type I had created, so I edited the model as outlined here: Backend customization - Strapi Developer Documentation
I then merged the feature branch I was on into the dev branch and then checked out the dev branch.
I then got 403 errors from the Strapi API in my NextJS project - turns out the previously set permissions had been deleted. In addition to this all the content I had entered into Strapi has completely disappeared. What has caused this? This behaviour is obviously a big red flag for the project - can’t afford for this to happen once the project is live.