First image as post cover

I did a blog when we had 'use first image as post cover' selected, but it used the second image as the post cover for the blog entry page, and also when autoposting to Facebook. So we deleted the first image and put it as the post cover and turned off the 'use the first image as post cover'. Now it is showing both the post cover image and another image on the blog entry page, and when it posted to facebook, there was no image showing.. just an empty placeholder. What am I doing wrong?