“Unexpected error” on update requests

Navigating WP admin in general tends to trigger multiple external requests, such as fetching news feeds and theme/plugin updates (not counting whatever plugin/themes might be doing on their own).

You can put configuration constants into wp-config.php to block external requests completely/partially:

define( 'WP_HTTP_BLOCK_EXTERNAL', true );
define( 'WP_ACCESSIBLE_HOSTS', 'api.wordpress.org,*.github.com' );

Or configure external requests to use your proxy settings:

define('WP_PROXY_HOST', '192.168.84.101');
define('WP_PROXY_PORT', '8080');
define('WP_PROXY_BYPASS_HOSTS', 'localhost, www.example.com, *.wordpress.org');

Plus WP_PROXY_USERNAME and WP_PROXY_PASSWORD for authentication.