The plugin is blocking editors from adding media to posts. When editors try to view media library from a post, the library appears empty. When they go to the media tab from the left menu, they can see the whole library. When editors try to upload a media file while editing a post, it uploads. But when they click insert to post, the post appears with no media inserted. When I deactivate the plugin, these problems go away. When I activate the plugin, all these problems come back.
I am also having a problem with Post-by-Email rejecting media, and I think it's related to this plugin, but that will require more experimentation before I can confirm.