Hi,
Thank you!
The issue was caused by something else, probably a 3rd party code or plugin. There is a filter applied on the get_terms hook, which removes some of the taxonomy terms when the plugin requests them. I put the following code to the functions.php file in your theme directory.
add_action('asp_pre_parse_filters', 'asp_remove_get_terms_filters', 10);
function asp_remove_get_terms_filters() {
remove_all_filters('get_terms');
}
I recommend keeping it there. It would be however better to locate the code causing the original issue.