Hi @timm
Could you please let me know the ACF version you are using?
I’ve tested it on my installation but failed to reproduce the issue. 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.
Also, could you try to pass the field groups key to the “field_groups” option like this:
'field_groups' => array('group_1'),
Thanks 🙂
