Work around https://core.trac.wordpress.org/ticket/28701

gistfile1.php

<?php

namespace HM\Hotfix;

add_action( 'deleted_option', __NAMESPACE__ . '\\workaround_28701' );

/**
 * Workaround cache deletion issue
 *
 * Ensures that the singular 
 * @link https://core.trac.wordpress.org/ticket/28701
 * @param string $option Option key
 */
function workaround_28701( $option ) {
	if ( defined( 'WP_INSTALLING' ) ) {
		return;
	}

	// Check alloptions
	// Uses array_key_exists instead of isset to detect the key
	$alloptions = wp_load_alloptions();
	if ( is_array( $alloptions ) && array_key_exists( $option, $alloptions ) ) {
		unset( $alloptions[$option] );
		wp_cache_set( 'alloptions', $alloptions, 'options' );
	}

	// Always clear the option key
	wp_cache_delete( $option, 'options' );
}