apache error

so my website got real slow suddenly, i checked the logs and it was this plugin :'(

Got error ‘PHP message: PHP Warning: substr() expects pa
rameter 1 to be string, array given in /bitnami/wordpress/wp-content/plugins/cost-of-goods-for-woocommerce/includes/alg-wc-cog-functions.php on line 40’, referer: https://****.com/wp-admin/edit.php?post_status=wc-processing&post_type=shop_order

the error was repeated several times