Send customer notification emails for merchandise orders, but not for FooEvents tickets

Question

I am hosting a webshop selling both merchandise and event tickets, using WooCommerce in combination with FooEvents.

I am having issues with the 'customer order completed' emails:

• I want to send them for Merchandise items (order ready to pick up)
• but do not want to send them for tickets (since these are issued automatically by email)

I tried to conditionally send the email notification based on the product categories, based on the following code:

(taken from this post: Avoid customer email notification for a specific product category in Woocommerce)

add_filter( 'woocommerce_email_recipient_customer_completed_order', 'product_cat_avoid_processing_email_notification', 10, 2 );

function product_cat_avoid_processing_email_notification( $recipient, $order ) {
    if( is_admin() ) return $recipient;

    // HERE set your product categories (coma separated term Ids, slugs or names)
    $cat_to_filter = 'tickets';
        

    // Loop through order items
    foreach ( $order->get_items() as $item ) {
        // Get an instance of the WC_Product object
        $product = $item->get_product(); 
        // Get the correct product ID (for variations we take the parent product ID)
        $product_id = $product->is_type('variation') ? $product->get_parent_id() : $product->get_id();

        // Check for product categories for this item
        if( has_term( $cat_to_filter, 'product_cat', $product_id ) )
            return ''; // If it's found, we return an empty recipient
    }
    return $recipient;
}

This code works fine for excluding orders with regular products, e.g. I can exclude order completed notifications for the product category 'merchandise'. However, for tickets it does not work and results in an error: a generic error message on checkout page, the order is created but tickets are not generated nor sent.

My hunch is, that the code does not work with FooEvents, either because:

• the code deletes the customer email address FooEvents needs to send the tickets, or
• the code interferes with FooEvents in the area of changing order statusses to 'completed'

Can you help me out and provide me a fix for this issue?

Thanks,

Jeroen