Fatal error from this plugin when duplicating a product

When I try to duplicate a product in Products (trying to minimize time spent adding variations), your plugin causes the fatal error below….

Fatal error: Uncaught Error: Cannot unset string offsets in /home/customer/www/buyidtags.com/public_html/wp-content/plugins/woocommerce-products-designer/includes/functions.php:607
Stack trace:
#0 /home/customer/www/buyidtags.com/public_html/wp-content/plugins/woocommerce-products-designer/admin/class-wpd-product.php(437): wpd_replace_key_in_array(”, 472, 2088)
#1 /home/customer/www/buyidtags.com/public_html/wp-includes/class-wp-hook.php(286): WPD_Product->duplicate_product_metas(Object(WC_Product_Variable), Object(WC_Product_Variable))
#2 /home/customer/www/buyidtags.com/public_html/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(”, Array)
#3 /home/customer/www/buyidtags.com/public_html/wp-includes/plugin.php(465): WP_Hook->do_action(Array)
#4 /home/customer/www/buyidtags.com/public_html/wp-content/plugins/woocommerce/includes/admin/class-wc-admin-duplicate-product.php(120): do_action(‘woocommerce_pro…’, Object(WC_Product_Variable), Object(WC_Product_Variable))
#5 /home/customer/www/buyidtags.com/public_ht in /home/customer/www/buyidtags.com/public_html/wp-content/plugins/woocommerce-products-designer/includes/functions.php on line 607