I had same issue, but I fork the git repo https://github.com/elliotcondon/acf to review the code. In the file field_group.php -> function get_fields appear the query that display the fields in the ACF settings. For any reason when I pass the second parameters directly and diplay the next error
WordPress database error: [ERROR: unterminated quoted string at or near “‘field\_” LINE 1: …M wp_postmeta WHERE post_id = 29 AND meta_key ILIKE ‘field\_ ^]
SELECT meta_key FROM wp_postmeta WHERE post_id = 29 AND meta_key LIKE ‘field\_
For this reason add to: SELECT meta_key FROM $wpdb->postmeta WHERE post_id = %d AND meta_key LIKE 'field\_%%'
add this to the code
SELECT meta_key FROM $wpdb->postmeta WHERE post_id = %d AND meta_key LIKE 'field\_%%'
check this out here https://github.com/patojimenez/acf/compare/elliotcondon:master…master
Pdt: Sorry my english is very bad, but I have to share this solution.