try to use a new WP_Query, when you use get_posts you’re using the main WP_Query this has hooks that other plugins can use to alter the query.
something else i saw is that you’re using include key which is not valid
$my_query = new WP_Query( array(
'post__in' => array( 1633, 1634, 1635 ),
'post_status' => 'any',
'post_type' => 'attachment',
'post_mime_type' => 'image',
'order' => 'ASC',
'orderby' => 'post__in'
) );