string(2) "id" Notice: id was called incorrectly. Product properties should not be accessed directly. Backtrace:

wp-content/themes/Active-Theme/woocommerce/single-product/related.php

/*if ( ! $related = $product->get_related( $posts_per_page ) ) {
    return;
}*/

$related = wc_get_related_products( $product->get_id(), $posts_per_page );

if ( ! $related ) {
  return;
}

$args = apply_filters( 'woocommerce_related_products_args', array(
'post_type'            => 'product',
'ignore_sticky_posts'  => 1,
'no_found_rows'        => 1,
'posts_per_page'       => $posts_per_page,
'orderby'              => $orderby,
'post__in'             => $related,
'post__not_in'         => array( $product->get_id() )
) );

This is probabily caused by an old file in yout template while you have a new Woocommerce version. The fix is quite easy, just look for the file "/themes/demo-theme/woocommerce/single-product/related.php" as described in the stack trace and replace:

$product->id;

with:

$product->get_id();

That should be done for all the occurrences of "$product->id;" in order to get rid of the warning