That should not happen during saving, license/update checks are only triggered on the plugins page periodically.
During the save process only the settings are put to the database via a regular Post method.
This issue sounds more like a problem with the actual firewall, maybe it catches something in the request as a false positive and simply blocks the request. From the error message it sounds like the firewall tries to access the wpewaf.com domain for some reason, and because it fails, it blocks the request alltogether.
You can try to add this to the wp-config.php file in your root directory:
define( 'ASP_BLOCK_EXTERNAL', true );
This will prevent any periodical update checks. If it was related to the problem, it may resolve it.