To be honest, I’m a little confused whey your are doing this
$field = get_field_object( 'custom_field) );
$value = get_post_meta( $post_id, 'custom_field', true );
echo $field['choices'][ $value ];
Why get the field object, then get the meta value and then output echo the label.
Set the field to either return the label or to return and array with value/label and then use
// set to return label
the_field('custom_field')
or
// set to return both
$value = get_field('custom_field');
echo $value['lable'];
back to your question. If the values choices are not being set when you call get_field_object() then that means that your filter is not being called. Where/in what file/when is your load filter being called?
