Oh, I see. That’s because of the security check – we’re using sanitize_title() function and we’re not going to change that. However you can do so on your own risk – line 839 includes/settings.php
Change this:
$input['news_slug'] = sanitize_title($input['news_slug']);
to something less sctrict:
$input['news_slug'] = sanitize_text_field($input['news_slug']);
