cdbtech

I’m seeing the same issue. It looks like it’s caused by class-wcpdf-admin.php:1402 sort_orders_by_numeric_invoice_number()

if ( ! is_admin() || ! $query->is_main_query() || 'shop_order' !== $query->get( 'post_type' ) && '_wcpdf_invoice_number' !== $query->get( 'meta_key' ) ) {
	return;
}

is probably supposed to be:

if ( ! is_admin() || ! $query->is_main_query() || 'shop_order' !== $query->get( 'post_type' ) || '_wcpdf_invoice_number' !== $query->get( 'meta_key' ) ) {
	return;
}

The incorrect AND is causing all queries to use meta_value_num, instead of just queries sorted by invoice number.

Would appreciate a quick patch for the issue. Thanks.