I’m having a similar problem. Using a custom taxonomy and a select in a repeater. The taxonomies is not showing up (even when I’m logged out), the select element is empty, works in admin.
I’m using the latest version of ACF Pro.
The error-log generated the following:
[19-Jul-2018 10:46:02 Europe/Stockholm] PHP Notice: Undefined property: WP_Error::$term_id in C:\www\site-name\wp-content\plugins\advanced-custom-fields-pro\includes\fields\class-acf-field-taxonomy.php on line 658
[19-Jul-2018 10:46:02 Europe/Stockholm] PHP Notice: Undefined property: WP_Error::$term_id in C:\www\site-name\wp-content\plugins\advanced-custom-fields-pro\includes\fields\class-acf-field-taxonomy.php on line 257
