[Waiting for user feedback] WPC Composite Products

This has been escalated to our Compatibility team and may take some debugging time, I'll get back to you as soon as I have any news or questions for you.

Our 2nd-tier support team confirmed that all `wooco_*` custom fields must be set to “COPY” in WPML.
https://wpml.org/documentation/getting-started-guide/translating-custom-fields/#how-to-translate-custom-fields

This ensures that the WooCommerce Composite Product data is correctly synchronized across translated products.

You also need to add the following code to your functions.php file:

if ( class_exists('Sitepress') ) { 
    add_filter( 'wooco_get_product_id', function( $product_id, $id ) {

        $type = get_post_type( $product_id );
        $element_type = ( $type === 'product_variation' ) ? 'product_variation' : 'product';
        $current_lang = apply_filters( 'wpml_current_language', null );
        $product_id = apply_filters( 'wpml_object_id', $product_id, $element_type, true, $current_lang );

        return (int) $product_id;
    }, 10, 2 );
}

This fix ensures that WooCommerce Composite Products correctly retrieve the matching product IDs in the current language, preventing mismatches or missing components when switching between translations.

Please let me know if it works on your site! After you make these changes, make sure to update both original product and its translation.

Ok, as in addition to custom field settings, the code is needed too.

In the custom fields you don't add code, only change translation preferences.

It is done on:
- Go to WPML → Settings.
- Scroll down to the Custom Fields Translation section.
-Set a translation preference for each custom field.

https://wpml.org/documentation/getting-started-guide/translating-custom-fields/#how-to-translate-custom-fields