By default I have "Publish Post to Facebook" disabled as I don't want all posts published.
When I create a post I want published I then enable "Publish Post to Facebook" and set the "Facebook Post Attribute line". I then either save to drafts, or schedule the post.
When I then leave the page and come back, these settings have often unset themselves. Sometimes they stay set, but if I come back and edit the post at a later stage they often come unset when I save.
This leads to a lot of situations where my scheduled post is published, but not pushed to Facebook.