Previews not working for drafts

I’ve just inherited a theme built on top of Timber, and I’m fairly unfamiliar with how Timber works. I can’t seem to preview posts that are drafts (published posts can be previewed just fine). The posts are routed to use /news – here’s the code for that:

Not sure why drafts can’t be previewed, does it have anything to do with how the routing is set up? Thank you for helping out and taking a look.

// News
		Timber::add_route('news/', function($params){

			//make a custom query based on incoming path and run it...
			$query = array(
				'posts_per_page' => 6,
				'post_type' => array('post'), //array('post','quote'),
				'paged' => 0
			);

			// pass special params
			$params['page_location'] = 'news';

			//load up a template which will use that query
			Timber::load_template(
				get_theme_root() . '/gimlet/index.php',
				$query,
				200,
				$params
			);
		});

		// News Pagination
		Timber::add_route('news/:pg', function($params){

			//make a custom query based on incoming path and run it...
			$query = array(
				'posts_per_page' => 6,
				'post_type' => array('post','quote'),
				'paged' => $params['pg']
			);

			// pass special params
			$params['page_location'] = 'news';

			//load up a template which will use that query
			Timber::load_template(
				get_theme_root() . '/gimlet/index.php',
				$query,
				200,
				$params
			);
		});

https://ww.wp.xz.cn/plugins/timber-library/