So I think I managed to fix this for me… Apparently the jQuery version & jQuery migrate was colliding with the version used when enqueueing scripts from ACF / WordPress. It gave no errors so I didn’t catch it at first. So I excluded my version of jQuery & Migrate from the specific templates and now it’s working as intended. I hope it helps!
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