Hey thanks for the response, a few things.
1 – The field works when it’s only 1 relationship. The site has thousands of posts so I started to think it was something related to ACF doing bad requests that caused timeout somehow.
2 – I’ve deactivated all the plugins and switched the theme to test, and I still can see the issue.
3 – Did u check the PHP error from the logs I posted? Or do you think it is not related at all?
Thanks
