jesshilario

Hello! I fixed the problem in the following way:

In the /wp-content/plugins/woocommerce/includes/wc-core-functions.php file:

1517 /**
1518  * User to sort checkout fields based on priority with uasort.
1519  *
1520  * @since 3.5.1
1521  * @param array $a First field to compare.
1522  * @param array $b Second field to compare.
1523  * @return int
1524 */
1525 function wc_checkout_fields_uasort_comparison( $a, $b ) {
1526         if(!isset($a['priority'])) $a['priority'] = 0; // Add this
1527         if(!isset($b['priority'])) $b['priority'] = 0; // Add this
1528         return wc_uasort_comparison( $a['priority'] , $b['priority'] );
1529 }

I know it’s not the right thing but the solution of @jobthomas did not work for me. I think it may be a temporary solution while the update arrives.

Regards!