API returns Internal Server Error when requested by anonymous user.

I was getting this too but only when pointing urls to existing paths. For instance Drupal has an existing `/about` page and I put that path into the url, there was this error. If I made it to a non-existent path `/about-2` it works as expected.

Did you happen to resolve this?

I had to turn off rules module. Not quite sure why this resolved the issue.

This module adds a route with access set to TRUE and if I install standard and make a request to jsonapi/menu_items/main as the anonymous user I get the expected response - a 200 with the menu links in. If I request for a non-existent main I get the expected 404.