Hi @raheem
This issue mostly causes by a custom query set somewhere in your plugin or theme. This custom query usually tries to change something but doesn’t check if it’s querying ACF’s data or not. The result is ACF fails to get the data needed to parse the returned result.
Could you please try to reproduce the issue on one of the WordPress’ stock themes (like Twenty Sixteen) with other plugins deactivated? If it disappears, then you can activate the theme and plugins one by one to see which one causes the issue.
I hope this makes sense. Thanks!
