Confirming this 'core_updater.lock'. It may not be obvious at first but look at the line 771.
File: wp-admin/includes/class-wp-upgrader.php
754: /**
755: * Creates a lock using WordPress options.
756: *
757: * @since 4.5.0
758: * @access public
759: * @static
760: *
761: * @param string $lock_name The name of this unique lock.
762: * @param int $release_timeout Optional. The duration in seconds to respect an existing lock.
763: * Default: 1 hour.
764: * @return bool False if a lock couldn't be created or if the lock is no longer valid. True otherwise.
765: */
766: public static function create_lock( $lock_name, $release_timeout = null ) {
767: global $wpdb;
768: if ( ! $release_timeout ) {
769: $release_timeout = HOUR_IN_SECONDS;
770: }
771: $lock_option = $lock_name . '.lock';
772:
773: // Try to lock.
774: $lock_result = $wpdb->query( $wpdb->prepare( "INSERT IGNORE INTO `$wpdb->options` ( `option_name`, `option_value`, `autoload` ) VALUES (%s, %s, 'no') /* LOCK */", $lock_option, time() ) );
775:
Now, if you like you may delete this option:
$>wp option delete my_option