In the following files, you must use the post_class() function to output the post class. If you need custom classes, you can pass them in directly, such as post_class( 'post-content example' ) or filter the post_class hook.
post_class( 'post-content example' )
We should've caught this in the first round, but it's not something we usually manually check because the WP Theme Check plugin typically picks it up. It didn't notice it because you use post_class() elsewhere in the theme.
Fixed in: 188b1d6