Not sure why it’s happening but resolved it with preg_replace 🙂 ..
add_action( 'forminator_post_data_field_post_saved', function( $post_id ){
$_POST['forminator_post_id'] = $post_id;
add_filter( 'forminator_replace_form_data', function( $content, $data, $fields ){
if( ! empty( $_POST['forminator_post_id'] ) && false !== strpos( $content, '[post_url]' ) ){
$link = preg_replace('#^https?://#i', '', get_permalink( $_POST['forminator_post_id'] ));
$content = str_replace( '[post_url]', $link, $content );
}
return $content;
}, 10, 3 );
} );