I followed the code a litte bit more.
in ‘api-helpers.php’ in function ‘acf_get_valid_terms’ my value is int(29) before this code:
// attempt to find new terms
foreach( $terms as $i => $term_id ) {
$new_term_id = wp_get_split_term($term_id, $taxonomy);
if( $new_term_id ) {
$terms[ $i ] = $new_term_id;
}
}
and int(618) after it. but i still don’t know why..
[edit]
Output of wp_get_split_term(29, 'post_tag')
is 618. So i guess my term database table is broken?