Rank Math SEO - Product and Post primary categories are not synchronize to translations

Overview of the issue

When using the Rank Math SEO plugin, the primary category set for a product or post in the default language does not synchronize to its translations. This issue persists even if you set the rank_math_primary_product_cat custom field as copy.

Workaround

Please, make sure of having a full backup of your site before proceeding.

• Open theme's functions.php file.
• Add the following code:

  // compsupp-6580: sync primary term and primary product terms for Rank Math
  add_filter('get_post_metadata', 'compsupp6580_filter_the_post_metadata', 20, 4);
  
  function compsupp6580_filter_the_post_metadata($value, $postId, $key, $single)
  {
  
  	$meta_keys_mapping = array(
  		'rank_math_primary_category'    => 'category',
  		'rank_math_primary_product_cat' => 'product_cat',
  	);
  
  	if (in_array($key, array_keys($meta_keys_mapping), true)) {
  		remove_filter('get_post_metadata', 'compsupp6580_filter_the_post_metadata', 20);
  		$value = get_post_meta($postId, $key, true);
  		add_filter('get_post_metadata', 'compsupp6580_filter_the_post_metadata', 20, 4);
  
  		$args     = [
  			'element_id'   => $postId,
  			'element_type' => get_post_type($postId),
  		];
  		$language = apply_filters('wpml_element_language_code', false, $args);
  		$value    = apply_filters('wpml_object_id', $value, $meta_keys_mapping[$key], true, $language);
  
  		if (!$single) {
  			$value = [$value];
  		}
  	}
  
  	return $value;
  }