would it make a difference if you use this array instead of the track_url direct?
$track = get_sub_field('track_url');
//if you use data-array instead of data-url at file return
//$track_url = get_sub_field('track_url') ;
//$track = $track_url['url'];
$attr = array(
'src' => $track ,
'loop' => '',
'autoplay' => '',
'preload' => 'none'
);
echo wp_audio_shortcode( $attr );