On websites hosted at Pantheon servers, there is a configuration file at the root directory of WordPress called wp-config-pantheon.php.
That’s the file where all your site’s database information is stored, and also these two parameters are configured there:
define('WP_HOME', $scheme . '://' . $_SERVER['HTTP_HOST']);
define('WP_SITEURL', $scheme . '://' . $_SERVER['HTTP_HOST']);
When this file gets cloned to the staging site’s directory, these two lines must be commented, as we already define them in the wp-config.php file with the correct value for the staging site.
So you will need to modify this file at the staging site’s directory wp-config-pantheon.php.
Just add // in front of each line of the above, so they should be like:
//define('WP_HOME', $scheme . '://' . $_SERVER['HTTP_HOST']);
//define('WP_SITEURL', $scheme . '://' . $_SERVER['HTTP_HOST']);